Formation of discontinuous films during an imprint lithography process

ABSTRACT

The present invention is directed to a template having a body including a surface with first and second regions. The first region has first wetting characteristics for a given material and the second region has second wetting characteristics for the given material. The first wetting characteristics differ from the second wetting characteristics. Specifically, the first region is formed from a surface treatment layer with a first surface energy to provide the first wetting characteristics. The second region is exposed portions of the body, typically quartz of fused silica, having a second surface energy associated therewith. The second surface energy is greater than the first surface energy to provide the second region with the second wetting characteristics.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 10/194,411, filed Jul. 11, 2002, entitled “Formation OfDiscontinuous Films During An Imprint Lithography Process” listingByung-Jin Choi, Sidlgata V. Sreenivasan, Mario J. Meissl and Michael P.C. Watts as inventors, which application is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments presented herein relate to methods and systems for imprintlithography. More particularly, embodiments relate to templates formicro- and nano-imprint lithography processes.

2. Description of the Relevant Art

Optical lithography techniques are currently used to make mostmicroelectronic devices. However, it is believed that these methods arereaching their limits in resolution. Sub-micron scale lithography hasbeen a critical process in the microelectronics industry. The use ofsub-micron scale lithography allows manufacturers to meet the increaseddemand for smaller and more densely packed electronic circuits on chips.It is expected that the microelectronics industry will pursue structuresthat are as small or smaller than about 50 nm. Further, there areemerging applications of nanometer scale lithography in the areas ofopto-electronics and magnetic storage. For example, photonic crystalsand high-density patterned magnetic memory of the order of terabytes persquare inch may require sub-100 nanometer scale lithography.

For making sub-50 nm structures, optical lithography techniques mayrequire the use of very short wavelengths of light (e.g., about 13.2nm). At these short wavelengths, many common materials are not opticallytransparent and therefore imaging systems typically have to beconstructed using complicated reflective optics. Furthermore, obtaininga light source that has sufficient output intensity at these wavelengthsis difficult. Such systems lead to extremely complicated equipment andprocesses that may be prohibitively expensive. It is also believed thathigh-resolution e-beam lithography techniques, though very precise, aretoo slow for high-volume commercial applications.

Several imprint lithography techniques have been investigated as lowcost, high volume manufacturing alternatives to conventionalphotolithography for high-resolution patterning. Imprint lithographytechniques are similar in that they use a template containing topographyto replicate a surface relief in a film on the substrate. One form ofimprint lithography is known as hot embossing.

Hot embossing techniques face several challenges: i) pressure greaterthan 10 MPa are typically required to imprint relief structures, ii)temperatures must be greater than the T_(g) of the polymer film, iii)patterns (in the substrate film) have been limited to isolation trenchesor dense features similar to repeated lines and spaces. Hot embossing isunsuited for printing isolated raised structures such as lines and dots.This is because the highly viscous liquids resulting from increasing thetemperature of the substrate films require extremely high pressures andlong time durations to move the large volume of liquids needed to createisolated structures. This pattern dependency makes hot embossingunattractive. Also, high pressures and temperatures, thermal expansion,and material deformation generate severe technical challenges in thedevelopment of layer-to-layer alignment at the accuracies needed fordevice fabrication. Such pattern placement distortions lead to problemsin applications such as patterned magnetic media for storageapplications. The addressing of the patterned medium bit by theread-write head becomes very challenging unless the pattern placementdistortions can be kept to a minimum.

SUMMARY OF THE INVENTION

A template having a body including a surface with first and secondregions. The first region has first wetting characteristics for thegiven material. The first wetting characteristics differ from the secondwetting characteristics. Specifically, the first region is formed from asurface treatment layer with a first surface energy to provide the firstwetting characteristics. The second region is exposed portions of thebody, typically quartz or fused-silica, having a second surface energyassociated therewith. The second surface energy is greater than thefirst surface energy to provide the second region with the secondwetting characteristics. These and other embodiments are discussed morefully below.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to theaccompanying drawings in which:

FIG. 1 depicts an embodiment of a system for imprint lithography;

FIG. 2 depicts an imprint lithography system enclosure;

FIG. 3 depicts an embodiment of an imprint lithography head coupled toan imprint lithography system;

FIG. 4 depicts a projection view of an imprint head;

FIG. 5 depicts an exploded view of an imprint head;

FIG. 6 depicts a projection view of a first flexure member;

FIG. 7 depicts a projection view of a second flexure member;

FIG. 8 depicts a projection view of first and second flexure memberscoupled together;

FIG. 9 depicts a projection view of a fine orientation system coupled toa pre-calibration system of an imprint head;

FIG. 10 depicts a cross-sectional view of a pre-calibration system;

FIG. 11 depicts a schematic diagram of a flexure system;

FIG. 12 depicts a projection view of a motion stage and an imprint headof an imprint lithography system;

FIG. 13 depicts a schematic diagram of a liquid dispense system;

FIG. 14 depicts a projection view of an imprint head with a light sourceand camera optically coupled to the imprint head;

FIGS. 15 and 16 depict side views of an interface between a liquiddroplet and a portion of a template;

FIG. 17 depicts a cross-sectional view a first embodiment of templateconfigured for liquid confinement at the perimeter of the template;

FIG. 18 depicts a cross-sectional view a second embodiment of templateconfigured for liquid confinement at the perimeter of the template;

FIGS. 19A-19D depict cross-sectional views of a sequence of steps of atemplate contacting a liquid disposed on a substrate;

FIGS. 20A-20B depict top and cross-sectional views, respectively, of atemplate having a plurality of patterning areas;

FIG. 21 depicts a projection view of a rigid template support systemcoupled to a pre-calibration system of an imprint head;

FIG. 22 depicts an imprint head coupled to an X-Y motion system;

FIGS. 23A-23F depict cross-sectional views of a negative imprintlithography process;

FIGS. 24A-24D depict cross-sectional views of a negative imprintlithography process with a transfer layer;

FIGS. 25A-25D depict cross-sectional views of a positive imprintlithography process;

FIGS. 26A-26C depict cross-sectional views of a positive imprintlithography process with a transfer layer;

FIGS. 27A-27D depict cross-sectional views of a combined positive andnegative imprint lithography process;

FIG. 28 depicts a schematic of an optical alignment measuring devicepositioned over a template and substrate;

FIG. 29 depicts a scheme for determining the alignment of a templatewith respect to a substrate using alignment marks by sequentiallyviewing and refocusing;

FIG. 30 depicts a scheme for determining the alignment of a templatewith respect to a substrate using alignment marks and polarized filters;

FIG. 31 depicts a top view of an alignment mark that is formed frompolarizing lines;

FIGS. 32A-32C depict top views of patterns of curable liquid applied toa substrate;

FIGS. 33A-33C depict a scheme for removing a template from a substrateafter curing;

FIG. 34 depicts an embodiment of a template positioned over a substratefor electric field based lithography;

FIGS. 35A-35D depict a first embodiment of a process for formingnanoscale structures using contact with a template;

FIGS. 36A-36C depict a first embodiment of a process for formingnanoscale structures without contacting a template;

FIGS. 37A-37B depict a template that includes a continuous patternedconductive layer disposed on a non-conductive base;

FIG. 38 depicts a motion stage that includes a fine orientation system;

FIG. 39 depicts a motion stage having a substrate tilt module;

FIG. 40 depicts a schematic drawing of a substrate support;

FIG. 41 depicts a schematic drawing of an imprint lithography systemthat includes an imprint head disposed below a substrate support.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawing and will herein be described in detail. It shouldbe understood, however, that the drawings and detailed descriptionthereto are not intended to limit the invention to the particular formdisclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments presented herein generally relate to systems, devices, andrelated processes of manufacturing small devices. More specifically,embodiments presented herein relate to systems, devices, and relatedprocesses of imprint lithography. For example, these embodiments may beused for imprinting sub 100 nm features on a substrate, such as asemiconductor wafer. It should be understood that these embodiments mayalso be used to manufacture other kinds of devices including, but notlimited to: patterned magnetic media for data storage, micro-opticaldevices, micro-electro-mechanical system, biological testing devices,chemical testing and reaction devices, and X-ray optical devices.

Imprint lithography processes have demonstrated the ability to replicatehigh-resolution (sub-50 nm) images on substrates using templates thatcontain images as topography on their surfaces. Imprint lithography maybe used in patterning substrates in the manufacture of microelectronicdevices, optical devices, MEMS, opto-electronics, patterned magneticmedia for storage applications, etc. Imprint lithography techniques maybe superior to optical lithography for making three-dimensionalstructures such as micro lenses and T-gate structures. Components of animprint lithography system, including the template, substrate, liquidand any other materials that may affect the physical properties of thesystem, including but not limited to surface energy, interfacialenergies, Hamacker constants, Van der Waals' forces, viscosity, density,opacity, etc., are engineered to properly accommodate a repeatableprocess.

Methods and systems for imprint lithography are discussed in U.S. Pat.No. 6,334,960 to Willson et al. entitled “Step and Flash ImprintLithography” which is incorporated herein by reference. Additionalmethods and systems for imprint lithography are further discussed inU.S. patent applications: U.S. Ser. No. 09/908,455 filed Jul. 17, 2001(published as U.S. Publication No. 2002-0094496 A1), entitled “Methodand System of Automatic Fluid Dispensing for Imprint LithographyProcesses”; U.S. Ser. No. 09/907,512 filed Jul. 16, 2001 entitled“High-Resolution Overlay Alignment Methods and Systems for ImprintLithography”; U.S. Ser. No. 09/920,341 filed Aug. 1, 2001 (published asU.S. Publication No. 2002-0093122-A1), entitled “Methods forHigh-Precision Gap Orientation Sensing Between a Transparent Templateand Substrate for Imprint Lithography”; U.S. Ser. No. 09/934,248 filedAug. 21, 2001 (published as U.S. Publication No. 2002-0150398-A1)entitled “Flexure Based Macro Motion Translation Stage”; U.S. Ser. No.09/698,317 filed Oct. 27, 2000 (issued as U.S. Pat. No. 6,873,087)entitled “High-Precision Orientation Alignment and Gap Control Stagesfor Imprint Lithography Processes”; U.S. Ser. No. 09/976,681 filed Oct.12, 2001 (issued as U.S. Pat. No. 6,696,220), entitled “Template Designfor Room Temperature, Low Pressure Micro- and Nano-Imprint Lithography”;and U.S. Ser. No. 10/136,188 filed May 1, 2002 (published as U.S.Publication No. 2003-0205657-A1), entitled “Methods of Manufacturing aLithography Template,” all of which are incorporated herein byreference. Further methods and systems are discussed in the followingpublications, all of which are incorporated herein by reference, “Designof Orientation Stages for Step and Flash Imprint Lithography,” B. J.Choi, S. Johnson, M. Colburn, S. V. Sreenivasan, C. G. Willson, toappear in J. of Precision Engineering; “Large area high densityquantized magnetic disks fabricated using nanoimprint lithography,” W.Wu, B. Cui, X. Y. Sun, W. Zhang, L. Zhunag, and S. Y. Chou., J. Vac SciTechnol B 16 (6) 3825-3829 November-December 1998;“Lithographically-induced Self-assembly of Periodic Polymer MicropillarArrays,” S. Y. Chou, L. Zhuang, J Vac Sci Tech B 17 (6), 3197-3202, 1999and “Large Area Domain Alignment in Block Copolymer Thin Films UsingElectric Fields,” P. Mansky, J. DeRouchey, J. Mays, M. Pitsikalis, T.Morkved, H. Jaeger and T. Russell, Macromolecules 13, 4399 (1998).

System for Imprint Lithography

Overall System Description

FIG. 1 depicts an embodiment of imprint lithography system 3900. System3900 includes imprint head 3100. Imprint head 3100 is mounted to imprinthead support 3910. Imprint head 3100 is configured to hold patternedtemplate 3700. Patterned template 3700 includes a plurality of recessesthat define a pattern of features to be imprinted into a substrate.Imprint head 3100 or motion stage 3600 is further configured to movepatterned template 3700 toward and away from a substrate to be imprintedduring use. System 3900 also includes motion stage 3600. Motion stage3600 is mounted to motion stage support 3920. Motion stage 3600 isconfigured to hold a substrate and move the substrate in a generallyplanar motion about motion stage support 3920. System 3900 furtherincludes curing light system 3500 coupled to imprint head 3100.Activating light system 3500 is configured to produce a curing light anddirect the produced curing light through patterned template 3700 coupledto imprint head 3100. Curing light includes light at an appropriatewavelength to cure a polymerizable liquid. Curing light includesultraviolet light, visible light, infrared light, x-ray radiation andelectron beam radiation.

Imprint head support 3910 is coupled to motion stage support 3920 bybridging supports 3930. In this manner imprint head 3100 is positionedabove motion stage 3600. Imprint head support 3910, motion stage support3920 and bridging supports 3930 are herein collectively referred to asthe system “body.” The components of the system body may be formed fromthermally stable materials. Thermally stable materials have a thermalexpansion coefficient of less than about 10 ppm/° C. at about roomtemperature (e.g. 25° C.). In some embodiments, the material ofconstruction may have a thermal expansion coefficient of less than about10 ppm/° C., or less than 1 ppm/° C. Examples of such materials includesilicon carbide, certain alloys of iron, including but not limited to:certain alloys of steel and nickel (e.g., alloys commercially availableunder the name INVAR.®) and certain alloys of steel, nickel and cobalt(e.g., alloys commercially available under the name SUPER INVAR™).Additional examples of such materials include certain ceramics,including but not limited to: ZERODUR™. ceramic. Motion stage support3920 and bridging supports 3930 are coupled to a support table 3940.Support table 3940 provides a substantially vibration free support forthe components of system 3900. Support table 3940 isolates system 3900from ambient vibrations (e.g., due to works, other machinery, etc.).Motion stages and vibration isolation support tables are commerciallyavailable from Newport Corporation of Irvine, Calif.

As used herein, the “X-axis” refers to the axis that runs betweenbridging supports 3930. As used herein the “Y-axis” refers to the axisthat is orthogonal to the X-axis. As used herein the “X-Y plane” is aplane defined by the X-axis and the Y-axis. As used herein the “Z-axis”refers to an axis running from motion stage support 3920 to imprint headsupport 3910, orthogonal to the X-Y plane. Generally an imprint processinvolves moving the substrate, or imprint head 3100, along an X-Y planeuntil the proper position of the substrate with respect to the patternedtemplate is achieved. Movement of the template, or motion stage, alongthe Z-axis, will bring the patterned template to a position that allowscontact between the patterned template and a liquid disposed on asurface of the substrate.

Imprint lithography system 3900 may be placed in enclosure 3960, asdepicted in FIG. 2. Enclosure 3960 encompasses imprint lithographysystem 3900 and provides a thermal and air barrier to the lithographycomponents. Enclosure 3960 includes movable access panel 3962 thatallows access to the imprint head and motion stage when moved to an“open” position, as depicted in FIG. 2. When in a “closed” position, thecomponents of system 3900 are at least partially isolated from the roomatmosphere. Access panel 3962 also serves as a thermal barrier to reducethe effects of temperature changes within the room on the temperature ofthe components within enclosure 3960. Enclosure 3960 includes atemperature control system. A temperature control system is used tocontrol the temperature of components within enclosure 3960. In oneembodiment, temperature control system is configured to inhibittemperature variations of greater than about 1° C. within enclosure3960. In some embodiments, a temperature control system inhibitsvariations of greater than about 0.1° C. In one embodiment, thermostatsor other temperature measuring devices in combination with one or morefans may be used to maintain a substantially constant temperature withenclosure 3960.

Various user interfaces may also be present on enclosure 3960. Acomputer controlled user interface 3964 may be coupled to enclosure3960. User interface 3964 may depict the operating parameters,diagnostic information, job progress and other information related tothe functioning of the enclosed imprint system 3900. User interface 3964may also be configured to receive operator commands to alter theoperating parameters of system 3900. A staging support 3966 may also becoupled to enclosure 3960. Staging support 3966 is used by an operatorto support substrates, templates and other equipment during an imprintlithography process. In some embodiments, staging support 3966 mayinclude one or more indentations 3967 configured to hold a substrate(e.g., a circular indentation for a semiconductor wafer). Stagingsupport 3966 may also include one or more indentations 3968 for holdinga template.

Additional components may be present depending on the processes that theimprint lithography system is designed to implement. For example, forsemiconductor processing equipment including, but not limited to, anautomatic wafer loader, an automatic template loader and an interface toa cassette loader (all not shown) may be coupled to imprint lithographysystem 3900.

Imprint Head

FIG. 3 depicts an embodiment of a portion of an imprint head 3100.Imprint head 3100 includes a pre-calibration system 3109 and a fineorientation system 3111 coupled to the pre-calibration system. Templatesupport 3130 is coupled to fine orientation system 3111. Templatesupport 3130 is designed to support and couple a template 3700 to fineorientation system 3111.

Referring to FIG. 4, a disk-shaped flexure ring 3124, which makes up aportion of the pre-calibration system 3109 is coupled to imprint headhousing 3120. Imprint head housing 3120 is coupled to a middle frame3114 with guide shafts 3112 a, 3112 b. In one embodiment, three (3)guide shafts may be used (the back guide shaft is not visible in FIG. 4)to provide a support for housing 3120. Sliders 3116 a and 3116 b coupledto corresponding guide shafts 3112 a, 3112 b about middle frame 3114 areused to facilitate the up and down motion of housing 3120. A disk-shapedbase plate 3122 is coupled to the bottom portion of housing 3120. Baseplate 3122 may be coupled to flexure ring 3124. Flexure ring 3124supports the fine orientation system components that include firstflexure member 3126 and second flexure member 3128. The operation andconfiguration of the flexure members 3126, 3128 are discussed in detailbelow.

FIG. 5 depicts an exploded view of imprint head 3700. As shown in FIG.5, actuators 3134 a, 3134 b, 3134 c are fixed within housing 3120 andcoupled to base plate 3122 and flexure ring 3124. In operation, motionof actuators 3134 a, 3134 b, and 3134 c controls the movement of flexurering 3124. Motion of actuators 3134 a, 3134 b, and 3134 c may allow fora coarse pre-calibration. In some embodiments, actuators 3134 a, 3134 b,and 3134 c may be equally spaced around housing 3120. Actuators 3134 a,3134 b, 3134 c and flexure ring 3124 together form the pre-calibrationsystem. Actuators 3134 a, 3134 b, 3134 c allow translation of flexurering 3124 along the Z-axis to control the gap accurately.

Imprint head 3100 also include a mechanism that enables fine orientationcontrol of template 3700 so that proper orientation alignment may beachieved and a uniform gap may be maintained by the template withrespect to a substrate surface. Alignment and gap control is achieved,in one embodiment, by the use of first and second flexure members, 3126and 3128, respectively.

FIGS. 6 and 7 depicted embodiments of first and second flexure members,3126 and 3128, respectively, in more detail. As depicted in FIG. 6,first flexure member 3126 includes a plurality of flexure joints 3160coupled to corresponding rigid bodies 3164 and 3166. Flexure joints 3160may be notch shaped to provide motion of rigid bodies 3164 and 3166about pivot axes that are located along the thinnest cross section ofthe flexure joints. Flexure joints 3160 and rigid body 3164 togetherform arm 3172, while additional flexure joints 3160 and rigid body 3166together form arm 3174. Arms 3172 and 3174 are coupled to and extendfrom first flexure frame 3170. First flexure frame 3170 has an opening3182, which allows curing light (e.g., ultraviolet light) to passthrough first flexure member 3126. In the depicted embodiment, fourflexure joints 3160 allow motion of first flexure frame 3170 about afirst orientation axis 3180. It should be understood, however, that moreor less flexure joints may be used to achieve the desired control. Firstflexure member 3126 is coupled to second flexure member 3128 throughfist flexure frame 3170, as depicted in FIG. 8. First flexure member3126 also includes two coupling members 3184 and 3186. Coupling members3184 and 3186 include openings that allow attachment of the couplingmembers to flexure ring 3124 using any suitable fastening means.Coupling members 3184 and 3186 are coupled to first flexure frame 3170via arms 3172 and 3174 as depicted.

Second flexure member 3128 includes a pair of arms 3202 and 3204extending from second flexure frame 3206, as depicted in FIG. 7. Flexurejoints 3162 and rigid body 3208 together form arm 3202, while additionalflexure joints 3162 and rigid body 3210 together form arm 3204. Flexurejoints 3162 may be notch shaped to provide motion of rigid bodies 3210and 3204 about pivot axes that are located along the thinnest crosssection of the flexure joints. Arms 3202 and 3204 are coupled to andextend from template support 3130. Template support 3130 is configuredto hold and retain at least a portion of a patterned template. Templatesupport 3130 also has an opening 3212, which allows curing light (e.g.,ultraviolet light) to pass through second flexure member 3128. In thedepicted embodiment, four flexure joints 3162 allow motion of templatesupport 3130 about a second orientation axis 3200. It should beunderstood, however, that more or less flexure joints may be used toachieve the desired control. Second flexure member 3128 also includesbraces 3220 and 3222. Braces 3220 and 3222 include openings that allowattachment of the braces to portions of first flexure member 3126.

In one embodiment, first flexure member 3126 and second flexure member3128 are joined as shown in FIG. 8 to form fine orientation system 3111.Braces 3220 and 3222 are coupled to first flexure frame 3170 such thatthe first orientation axis 3180 of first flexure member 3126 and secondorientation axis 3200 of second flexure member 3128 are substantiallyorthogonal to each other. In such a configuration, first orientationaxis 3180 and second orientation axis 3200 intersect at a pivot point3252 at approximately the center region of patterned template 3700disposed in template support 3130. This coupling of first and secondflexure members, 3126 and 3128 respectively, allows fine alignment andgap control of patterned template 3700 during use. While first andsecond flexure members 3126 and 3128 are depicted as discrete elements,it should be understood that the first and second flexure members may beformed from a single machined part where flexure members 3126 and 3128are integrated together. Flexure members 3126 and 3128 are coupled bymating of surfaces such that motion of patterned template 3700 occursabout pivot point 3252, substantially reducing “swinging” and othermotions that may shear imprinted features following imprint lithography.Fine orientation system 3111 imparts negligible lateral motion at thetemplate surface and negligible twisting motion about the normal to thetemplate surface due to selectively constrained high structuralstiffness of the flexure joints. Another advantage of using the hereindescribed flexure members is that they do not generate substantialamounts of particles, especially when compared with frictional joints.This offers an advantage for imprint lithography processes, as particlesmay disrupt such processes.

FIG. 9 depicts the assembled fine orientation system 3111 coupled to thepre-calibration system. Patterned template 3700 is positioned withintemplate support 3130 that is part of second flexure member 3128. Secondflexure member 3128 is coupled to first flexure member 3126 in asubstantially orthogonal orientation. First flexure member 3124 iscoupled to flexure ring 3124 via coupling members 3186 and 3184. Flexurering 3124 is coupled to base plate 3122, as has been described above.

FIG. 10 represents a cross-section of the pre-calibration system lookingthrough cross-section 3260. As shown in FIG. 10, flexure ring 3124 iscoupled to base plate 3122 with actuator 3134. Actuator 3134 includesend 3270 coupled to force detector 3135 that contacts flexure ring 3124.During use activation of actuator 3134 causes movement of end 3270toward or away from flexure ring 3124. The movement of end 3270 towardflexure ring 3124 induces a deformation of flexure ring 3124 and causestranslation of fine orientation system 3111 along the Z-axis toward thesubstrate. Movement of base 3270 away from flexure ring 3124 allowsflexure ring 3124 to move to its original shape and, in the process,moves fine orientation stage 3111 away from the substrate.

In a typical imprint process the template is disposed in a templateholder coupled to fine orientation system 3111, as depicted in previousfigures. The template is brought into contact with a liquid on a surfaceof a substrate. Compression of the liquid on the substrate as thetemplate is brought closer to the substrate causes a resistive force tobe applied by the liquid onto the template. This resistive force istranslated through fine orientation system 3111 and to flexure ring 3124as shown in both FIGS. 9 and 10. The force applied against flexure ring3124 will also be translated as a resistive force to actuators 3134. Theresistive force applied to actuator 3134 may be determined using forcesensor 3135. Force sensor 3135 may be coupled to actuator 3134 such thata resistive force applied to actuator 3135 during use may be determinedand controlled.

FIG. 11 depicts a flexure model, denoted generally as 3300, useful inunderstanding the principles of operation of a fine decoupledorientation stage, such as the fine orientation section describedherein. Flexure model 3300 may include four parallel joints: Joints 1,2, 3 and 4, that provide a four-bar-linkage system in its nominal androtated configurations. Line 3310 denotes an axis of alignment of Joints1 and 2. Line 3312 denotes an axis of alignment of Joints 3 and 4. Angle{acute over (α)}₁ represents an angle between a perpendicular axisthrough the center of template 3700 and line 3310. Angle {acute over(α)}₂ represents a perpendicular axis through the center of template3700 and line 3310. Angles {acute over (α)}₁ and {acute over (α)}₂, insome embodiments, are selected so that the compliant alignment axis (ororientation axis) lies substantially at the surface of template 3700.For fine orientation changes, rigid body 3314 between Joints 2 and 3 mayrotate about an axis depicted by Point C. Rigid body 3314 may berepresentative of template support 3130 of second flexure member 3128.

Fine orientation system generates pure tilting motions with nosubstantial lateral motions at the surface of a template coupled to thefine orientation system. The use of flexure arms may provide fineorientation system with high stiffness in the directions where sidemotions or rotations are undesirable and lower stiffness in directionswhere necessary orientation motions are desirable. Fine orientationsystem, therefore allows rotations of the template support, andtherefore the template, about the pivot point at the surface oftemplate, while providing sufficient resistance in a directionperpendicular to the template and parallel to the template to maintainthe proper position with respect to the substrate. In this manner apassive orientation system is used for orientation of the template to aparallel orientation with respect to a template. The term “passive”refers to a motion that occurs without any user or programmablecontroller intervention, i.e., the system self-corrects to a properorientation by contact of the template with the liquid. Alternateembodiments in which the motion of the flexure arms is controlled bymotors to produce an active flexure may also be implemented.

Motion of the fine orientation system may be activated by direct orindirect contact with the liquid. If the fine orientation system ispassive, then it is, in one embodiment, designed to have the mostdominant compliance about two orientation axes. The two orientation axeslie orthogonal to each other and lie on the imprinting surface of animprinting member disposed on the fine orientation system. The twoorthogonal torsional compliance values are set to be the same for asymmetrical imprinting member. A passive fine orientation system isdesigned to alter the orientation of the template when the template isnot parallel with respect to a substrate. When the template makescontact with liquid on the substrate, the flexure members compensate forthe resulting uneven liquid pressure on the template. Such compensationmay be affected with minimal or no overshoot. Further, a fineorientation system as described above may hold the substantiallyparallel orientation between the template and substrate for asufficiently long period to allow curing of the liquid.

Imprint head 3100 is mounted to imprint head support 3910 as depicted inFIG. 1. In this embodiment, imprint head 3910 is mounted such that theimprint head remains in a fixed position at all times. During use, allmovement along the X-Y plane is performed to the substrate by motionstage 3600.

Motion Stage

Motion stage 3600 is used to support a substrate to be imprinted andmove the substrate along an X-Y plane during use. Motion stage 3600, insome embodiments, is capable of moving a substrate over distances of upto several hundred millimeters with an accuracy of at least ±30 nm,preferably with an accuracy of about ±10 nm. In one embodiment, motionstage includes a substrate chuck 3610 that is coupled to carriage 3620,as depicted in FIG. 12. Carriage 3620 is moved about base 3630 on africtional bearing system or a non-frictional bearing system. In oneembodiment, a non-frictional bearing system that includes an air bearingis used. Carriage 3620 is suspended above base 3630 of motion stage 3600using, in one embodiment, an air layer (i.e., the “air bearing”).Magnetic or vacuum systems may be used to provide a counter balancingforce to the air bearing level. Both magnetic based and vacuum basedsystems are commercially available from a variety of suppliers and anysuch systems may be used in an imprint lithography process. One exampleof motion stage 3600 that is applicable to imprint lithography processesis the Dynam YX motion stage commercially available from NewportCorporation, Irvine Calif. Motion stage 3600 also may include a tip tiltstage similar to the calibration stage, designed to approximately levelthe substrate to the X-Y motion plane. It also may include one or moretheta stages to orient the patterns on the substrate to the X-Y motionaxes.

Liquid Dispenser

System 3900 also includes a liquid dispense system which is used todispense a curable liquid onto a substrate. Liquid dispense system iscoupled to the system body. In one embodiment, a liquid dispense systemis coupled to imprint head 3100. FIG. 3 depicts liquid dispenser head2507 of a liquid dispense system extending out from cover 3127 ofimprint head 3100. Various components of liquid dispense system 3125 maybe disposed in cover 3127 of imprint head 3100.

A schematic of a liquid dispense system is depicted in FIG. 13. In anembodiment, liquid dispense system 3125 includes liquid container 2501.Liquid container 2501 is configured to hold an activating light curableliquid. Liquid container 2501 is coupled to pump 2504 via inlet conduit2502. Inlet valve 2503 is positioned between liquid container 2501 andpump 2504 to control flow through inlet conduit 2502. Pump 2504 iscoupled to liquid dispenser head 2507 via outlet conduit 2506.

Liquid dispense system 3125 is configured to allow precise volumecontrol of the amount of liquid dispensed onto an underlying substrate.In one embodiment, liquid control is achieved using a piezoelectricvalve as pump 2504. Piezoelectric valves are available commercially fromthe Lee Company, Westbrook, Conn. During use, a curable liquid is drawninto pump 2504 through inlet conduit 2502. When a substrate is properlypositioned below, pump 2504 is activated to force a predetermined volumeof liquid through outlet conduit 2506. The liquid is then dispensedthrough liquid dispenser head 2507 onto the substrate. In thisembodiment, liquid volume control is achieved by control of pump 2504.Rapid switching of the pump from an open to closed state allows acontrolled amount of liquid to be sent to dispenser head 2507. Pump 2504is configured to dispense liquid in volumes of less than about 1 μL. Theoperation of pump 2504 may allow either droplets of liquid or acontinuous pattern of liquid to be dispensed onto the substrate.Droplets of liquid are applied by rapidly cycling pump 2504 from an opento closed state. A stream of liquid is produced on the substrate byleaving pump 2504 in an open state and moving the substrate under liquiddispenser head 2507.

In another embodiment, liquid volume control may be achieved by use ofliquid to liquid dispenser head 2507. In such a system, pump 2504 isused to supply a curable liquid to liquid dispenser head 2507. Smalldrops of liquid whose volume may be accurately specified are dispensedusing a liquid dispensing actuator. Examples of liquid dispensingactuators include micro-solenoid valves or piezo-actuated dispensers.Piezo-actuated dispensers are commercially available from MicroFabTechnologies, Inc., Plano, Tex. Liquid dispensing actuators areincorporated into liquid dispenser head to allow control of liquiddispensing. Liquid dispensing actuators are configured to dispensebetween about 50 pL to about 1000 pL of liquid per drop of liquiddispensed. Advantages of a system with a liquid dispensing actuatorinclude faster dispensing time and more accurate volume control. Liquiddispensing systems are further described in U.S. application Ser. No.09/908,455 filed Jul. 17, 2001 (now U.S. Publication No.2002-0094496-A1), entitled “Method and System of Automatic FluidDispensing for Imprint Lithography Processes” which is incorporatedherein by reference.

Coarse Measurement System

Coarse determination of the position of the template and the substrateis determined by the use of linear encoders (e.g., exposed linearencoders). Encoders offer a coarse measurement on the order of 0.01 μm.Linear encoders include a scale coupled to the moving object and areader coupled to the body. The scale may be formed from a variety ofmaterials including glass, glass ceramics, and steel. The scale includesa number of markings that are read by the reader to determine a relativeor absolute position of the moving object. The scale is coupled to themotion stage by means that are known in the art. A reader is coupled tothe body and optically coupled to the scale. In one embodiment, anexposed linear encoder may be used. Encoders may be configured todetermine the position of the motion stage along either a single axis,or in a two-axis plane. An example of an exposed two-axis linear encoderis the PP model encoder available from Heidenhain Corporation,Schaumburg, Ill. Generally, encoders are built into many commerciallyavailable X-Y motion stages. For example, the Dynam YX motion stageavailable from Newport Corp has a two-axis encoder built into thesystem.

The coarse position of the template along the Z-axis is also determinedusing a linear encoder. In one embodiment, an exposed linear encoder maybe used to measure the position of the template. A scale of the linearencoder, in one embodiment, is coupled to the pre-calibration ring ofthe imprint head. Alternatively, the scale may be coupled directly tothe template support 3130. The reader is coupled to the body andoptically coupled to the scale. Position of the template is determinedalong the Z-axis by use of encoders.

Air Gauges

In an embodiment, an air gauge 3135 may be coupled to imprint head 3100,as depicted in FIG. 3. Air gauge 3135 is used to determine whether asubstrate disposed on a motion stage is substantially parallel to areference plane. As used herein, an “air gauge” refers to a device thatmeasures the pressure of a stream of air directed toward a surface. Whena substrate is disposed under an outlet of air gauge 3135, the distancethe substrate is from the outlet of air gauge 3135 will influence thepressure the air gauge senses. Generally, the further away from the airgauge the substrate is, the lesser the pressure.

In such a configuration, air gauge 3135 may be used to determinedifferences in pressure resulting from changes in the distance betweenthe substrate surface and the air gauge. By moving air gauge 3135 alongthe surface of the substrate, the air gauge determines the distancebetween the air gauge and the substrate surface at the various pointsmeasured. The degree of planarity of the substrate with respect to theair gauge is determined by comparing the distance between the air gaugeand the substrate at the various points measured. The distance betweenat least three points on the substrate and the air gauge is used todetermine if a substrate is planar. If the distance is substantially thesame, the substrate is considered to be planar. Significant differencesin the distances measured between the substrate and the air gaugeindicate a non-planar relationship between the substrate and the airgauge. This non-planar relationship may be caused by the non-planarityof the substrate or a tilt of the substrate. Prior to use, a tilt of thesubstrate is corrected to establish a planar relationship between thesubstrate and the template using the tip tilt stage attached to the X Ystage. Suitable air gauges may be obtained from Senex Inc.

During use of air gauges, the substrate or template is placed within themeasuring range of the air gauge. Motion of the substrate toward the airgauge may be accomplished by either Z-axis motion of the imprint head orZ-axis motion of the motion stage.

Light Source

In an imprint lithography process, a light curable liquid is disposed ona surface of the substrate. A patterned template is brought into contactwith the light curable liquid and activating light is applied to thelight curable liquid. As used herein “activating light” means light thatmay affect a chemical change. Activating light may include ultravioletlight (e.g., light having a wavelength between about 200 nm to about 400nm), actinic light, visible light or infrared light. Generally, anywavelength of light capable of affecting a chemical change may beclassified as activating. Chemical changes may be manifested in a numberof forms. A chemical change may include, but is not limited to, anychemical reaction that causes a polymerization or a cross-linkingreaction to take place. The activating light, in one embodiment, ispassed through the template prior to reaching the composition. In thismanner the light curable liquid is cured to form structurescomplementary to the structures formed on the template.

In some embodiment, activating light source 3500 is an ultraviolet lightsource capable of producing light having a wavelength between about 200nm to about 400 nm. Activating light source 3500 is optically coupled tothe template as depicted in FIG. 1. In one embodiment, activating lightsource 3500 is positioned proximate to imprint head 3100. Imprint head3100 includes a mirror 3121 (depicted in FIG. 4, which reflects lightfrom the activating light source to the patterned template. Light passesthrough an opening in the body of imprint head 3100 and is reflected bymirror 3121 toward 3700. In this manner, activating light sourceirradiates a patterned template without being disposed in imprint head3100.

Most activating light sources produce a significant amount of heatduring use. If activating light source 3500 is too close to imprintlithography system 3900, heat from light source 3700 will radiate towardthe body of imprint system 3900 and may cause the temperature ofportions of the body to increase. Since many metals expand when heated,the increase in temperature of a portion of the body of imprint system3900 may cause an expansion of the body to expand. This expansion mayaffect the accuracy of imprint system 3900 when sub-100 nm features arebeing produced.

In one embodiment, activating light source is positioned at a sufficientdistance from the body such that system body is insulated from heatproduced by activating light source 3500 by the intervening air betweenactivating light source 3500 and imprint head 3100. FIG. 14 depicts anactivating light source 3500 optically coupled to imprint head 3100.Activating light source 3500 includes an optical system 3510 thatprojects light generated by a light source toward imprint head 3100.Light passes from optical system 3510 into imprint head 3100 via opening3123. Light is then reflected toward a template coupled to imprint head3110 by mirror 3121 disposed within the imprint head (see FIG. 4). Inthis manner, the light source is thermally insulated from the body. Asuitable light source may be obtained from OAI Inc, Santa Clara Calif.

Optical Alignment Devices

One or more optical measuring devices may be coupled to imprint head3910 and/or motion stage 3920. Generally, an optical measuring device isany device that allows the position and/or orientation of a templatewith respect to a substrate to be determined.

Turning to FIG. 14, a through-the-template optical imaging system 3800is optically coupled to imprint head 3100. Optical imaging system 3800includes optical imaging device 3810 and optical system 3820. Opticalimaging device 3810, in one embodiment, is a CCD microscope. Opticalimaging system 3800 is optically coupled to the template through imprinthead 3100. Optical imaging system 3800 is also optically coupled to asubstrate, when the substrate is disposed under the patterned template.Optical imaging system 3800 is used to determine the placement errorbetween a patterned template and an underlying substrate as describedherein. In one embodiment, mirror 3121 (depicted in FIG. 4) is movablewithin imprint head 3100. During an alignment or optical inspectionprocess, mirror 3121 is moved out of the optical path of optical imagingsystem 3800.

During use of an optical alignment device 3810, the substrate ortemplate is placed within the measuring range (e.g., the field of view)of air optical imaging system 3800. Motion of the substrate towardoptical imaging system 3800 may be accomplished by either Z-axis motionof imprint head 3100 or Z-axis motion of motion stage 3600.

Light Curable Liquid

As previously mentioned, a light curable liquid is placed on a substrateand a template is brought into contact with the liquid during an imprintlithography process. The curable liquid is a low viscosity liquidmonomer solution. A suitable solution may have a viscosity ranging fromabout 0.01 cps to about 100 cps (measured at 25° C.). Low viscositiesare especially desirable for high-resolution (e.g., sub-100 nm)structures. Low viscosities also lead to faster gap closing.Additionally, low viscosities result in faster liquid filling of the gaparea at low pressures. In particular, in the sub-50 nm regime, theviscosity of the solution should be at or below about 30 cps, or morepreferably below about 5 cps (measured at 25° C.).

Many of the problems encountered with other lithography techniques maybe solved by using a low viscosity light curable liquid in an imprintlithography process. Patterning of low viscosity light curable liquidssolves each of the issues facing hot embossing techniques by utilizing alow-viscosity, light-sensitive liquid. Also use of a thick, rigid,transparent template offers the potential for easier layer-to-layeralignment. The rigid template is, in general, transparent to both liquidactivating light and alignment mark measurement light.

The curable liquid may be composed of a variety of polymerizablematerials. Generally, any photopolymerizable material may be used.Photopolymerizable materials may include a mixture of monomers and aphotoinitiator. In some embodiments, the curable liquid may include oneor more commercially available negative photoresist materials. Theviscosity of the photoresist material may be reduced by diluting theliquid photoresist with a suitable solvent.

In an embodiment, a suitable curable liquid includes a monomer, asilylated monomer, and an initiator. A crosslinking agent and a dimethylsiloxane derivative may also be included. Monomers include, but are notlimited to, acrylate and methacylate monomers. Examples of monomersinclude, but are not limited to, butyl acrylate, methyl acrylate, methylmethacrylate, or mixtures thereof. The monomer makes up approximately 25to 50% by weight of the curable liquid. It is believed that the monomerensures adequate solubility of the photoinitiator in the curable liquid.It is further believed that the monomer provides adhesion to anunderlying organic transfer layer, when used.

The curable liquid may also include a silylated monomer. Silylatedmonomers in general are polymerizable compounds that include a silicongroup. Classes of silylated monomers include, but are not limited to,silane acrylyl and silane methacrylyl derivatives. Specific examplesinclude methacryloxypropyl tris(tri-methylsiloxy)silane and(3-acryloxypropyl)tris(trimethoxysiloxy)-silane. Silylated monomers maybe present in amounts from 25 to 50% by weight. The curable liquid mayalso include a dimethyl siloxane derivative. Examples of dimethylsiloxane derivatives include, but are not limited to, (acryloxypropyl)methylsiloxane dimethylsiloxane copolymer, acryloxypropyl methylsiloxanehomopolymer, and acryloxy terminated polydimethylsiloxane. Dimethylsiloxane derivatives are present in amounts from about 0 to 50% byweight. It is believed that the silylated monomers and the dimethylsiloxane derivatives may impart a high oxygen etch resistance to thecured liquid. Additionally, both the silylated monomers and the dimethylsiloxane derivatives are believed to reduce the surface energy of thecured liquid, therefore increasing the ability of the template torelease from the surface. The silylated monomers and dimethyl siloxanederivatives listed herein are all commercially available from Gelest,Inc.

Any material that may initiate a free radical reaction may be used asthe initiator. For activating light curing of the curable material, itis preferred that the initiator is a photoinitiator. Examples ofinitiators include, but are not limited to, alpha-hydroxyketones (e.g.,1-hydroxycyclohexyl phenyl ketone, sold by Ciba-Geigy Specialty ChemicalDivision as Irgacure 184), and acylphosphine oxide initiators (e.g.,phenylbis(2,4,6-trimethyl benzoyl) phosphine oxide, sold by Ciba-GeigySpecialty Chemical Division as Irgacure 819).

The curable liquid may also include a crosslinking agent. Crosslinkingagents are monomers that include two or more polymerizable groups. Inone embodiment, polyfunctional siloxane derivatives may be used as acrosslinking agent. An example of a polyfunctional siloxane derivativeis 1,3-bis(3 methacryloxypropyl)-tetramethyl disiloxane. In one example,a curable liquid may include a mixture of 50% by weight of n-butylacrylate and 50% (3-acryloxypropyl) tris-trimethylsiloxane-silane. Tothis mixture 3% by weight mixture of a 1:1 Irgacure 819 and Irgacure 184and 5% of the crosslinker 1,3-bis(3-methacryloxypropyl) tetramethyldisiloxane may be added. The viscosity of this mixture is less than 30cps measured at about 25° C.

Curable Liquid with Gas Release

In an alternate embodiment, the curable liquid may be formed of amonomer, an acid-generating photo-agent, and a base-generatingphoto-agent. Examples of the monomer include, but are not limited to,phenolic polymers and epoxy resins. The acid-generating photo-agent is acompound that releases acid when treated with activating light. Thegenerated acid catalyzes polymerization of the monomer. Those ofordinary skill in the art know such acid-generating additives, and thespecific acid-generating additive used depends on the monomer and thedesired curing conditions. In general, the acid-generating additive isselected to be sensitive to radiation at the first wavelength λ₁, which,in some implementations, is in the visible or near ultraviolet (near UV)range. For example, in some implementations, the first wavelength λ₁ isselected to be approximately 400 nm or longer. A base generatingphoto-agent is also added to the monomer. The base-generatingphoto-agent may inhibit curing of the monomer near the interface of thetemplate. The base generating photo-agent may be sensitive to radiationat a second wavelength λ₂, yet inert or substantially inert to radiationat the first wavelength λ₁. Moreover, the second wavelength λ₂ should beselected so that radiation at the second wavelength is primarilyabsorbed near the surface of the monomer at the interface with thetemplate and does not penetrate very far into the curable liquid. Forexample, in some implementations, a base generating additive that issensitive to radiation having a wavelength λ₂ in the deep UV range, inother words, radiation having a wavelength in the range of about 190-280nm, may be used.

According to an embodiment, a curable liquid that includes a monomer, anacid-generating photo-agent and a base-generating photo-agent isdeposited onto a substrate. A template is brought into contact with thecurable liquid. The curable liquid is then exposed to radiation at afirst wavelength λ₁ and a second wavelength λ₂ of light at substantiallythe same time. Alternatively, the curing liquid may be exposed to theradiation at the second wavelength λ₂ and subsequently to the radiationat the first wavelength λ₁. Exposure of the curable liquid to radiationat the second wavelength λ₂ produces an excess of base near theinterface with the template. The excess base serves to neutralize theacid that is produced by exposure of the curable liquid to radiation atthe first wavelength μ₁, thereby inhibiting the acid from curing thecurable liquid. Since the radiation at the second wavelength λ₂ has ashallow penetration depth into the curable liquid, the base produced bythat radiation only inhibits curing of the curable liquid at or near theinterface with the template. The remainder of the curable liquid iscured by exposure to the longer wavelength radiation (λ₁) whichpenetrates throughout the curable liquid. U.S. Pat. No. 6,218,316entitled “Planarization of Non-Planar Surfaces in Device Fabrication”describes additional details concerning this process and is incorporatedherein by reference.

In another embodiment, the curable liquid may include a photosensitiveagent which, when exposed, for example, to deep UV radiation, decomposesto produce one or more gases such as hydrogen (H₂), nitrogen (N₂),nitrous oxide (N₂O), sulfur tri-oxide (SO₃), acetylene (C₂H₂), carbondioxide (CO₂), ammonia (NH₃) or methane (CH₄). Radiation at a firstwavelength λ₁, such as visible or near UV, may be used to cure thecurable liquid, and the deep UV radiation (λ₂) may be used to produceone or more of the foregoing gases. The generation of the gases produceslocalized pressure near the interface between the cured liquid and thetemplate to facilitate separation of the template from the cured liquid.U.S. Pat. No. 6,218,316 describes additional details concerning thisprocess and is incorporated herein by reference.

In another embodiment, a curable liquid may be composed of a monomerthat cures to form a polymer that may be decomposed by exposure tolight. In one embodiment, a polymer with a doubly substituted carbonbackbone is deposited on the substrate. After the template is broughtinto contact with the curable liquid, the curable liquid is exposed toradiation at a first wavelength λ₁ (e.g., greater than 400 nm) andradiation at the second wavelength λ₂ in the deep UV range. Radiation atthe first wavelength serves to cure the curable liquid. When the curableliquid is exposed to the second wavelength λ₂, scission occurs at thesubstituted carbon atoms. Since deep UV radiation does not penetratedeeply into the curable liquid, the polymer decomposes only near theinterface with the template. The decomposed surface of the cured liquidfacilitates separation from the template. Other functional groups whichfacilitate the photo-decomposition of the polymer also can be used. U.S.Pat. No. 6,218,316 describes additional details concerning this processand is incorporated herein by reference.

Patterned Templates

In various embodiments, an imprint lithography template is manufacturedusing processes including, but not limited to, optical lithography,electron beam lithography, ion-beam lithography, x-ray lithography,extreme ultraviolet lithography, scanning probe lithography, focused ionbeam milling, interferometric lithography, epitaxial growth, thin filmdeposition, chemical etch, plasma etch, ion milling, reactive ion etchor a combination of the above. Methods for making patterned templatesare described in U.S. patent application Ser. No. 10/136,188 filed May1, 2002 entitled “Methods of Manufacturing a Lithography Template”,which is incorporated herein by reference.

In an embodiment, the imprint lithography template is substantiallytransparent to activating light. The template includes a body having alower surface. The template further includes a plurality of recesses onthe lower surface extending toward the top surface of the body. Therecesses may be of any suitable size, although typically at least aportion of the recesses has a feature size of less than about 250 nm.

With respect to imprint lithography processes, the durability of thetemplate and its release characteristics may be of concern. In oneembodiment, a template is formed from quartz. Other materials may beused to form the template and include, but are not limited to, silicongermanuim carbon, gallium nitride, silicon germanium, sapphire, galliumarsinide, epitaxial silicon, poly-silicon, gate oxide, silicon dioxideor combinations thereof. Templates may also include materials used toform detectable features, such as alignment markings. For example,detectable features may be formed of SiO_(X), where X is less than 2. Insome embodiments, X is about 1.5. In another example, detectablefeatures may be formed of a molybdenum silicide. Both SiO_(X) andmolybdenum silicide are optically transparent to light used to cure thepolymerizable liquid. Both materials, however, are substantially opaqueto visible light. Use of these materials allows alignment marks to becreated on the template that will not interfere with curing of theunderlying substrate.

As previously mentioned, the template is treated with a surfacetreatment material to form a thin layer on the surface of the template.A surface treatment process is optimized to yield a low surface energycoating. Such a coating is used in preparing imprint templates forimprint lithography. Treated templates have desirable releasecharacteristics relative to untreated templates. Untreated templatesurfaces possess surface free energies of about 65 dynes/cm or more. Atreatment procedure disclosed herein yields a surface treatment layerthat exhibits a high level of durability. Durability of the surfacetreatment layer allows a template to be used for numerous imprintswithout having to replace the surface treatment layer. The surfacetreatment layer, in some embodiments, reduces the surface free energy ofthe lower surface measured at 25° C. to less than about 40 dynes/cm, orin some cases, to less than about 20 dynes/cm.

A surface treatment layer, in one embodiment, is formed by the reactionproduct of an alkylsilane, a fluoroalkylsilane, or afluoroalkyltrichlorosilane with water. This reaction forms a silinatedcoating layer on the surface of the patterned template. For example, asilinated surface treatment layer is formed from a reaction product oftridecafluoro-1,1,2,2-tetrahydrooctyl trichlorosilane with water. Asurface treatment layer may be formed using either a liquid-phaseprocess or a vapor-phase process. In a liquid-phase process, thesubstrate is immersed in a solution of precursor and solvent. In avapor-phase process, a precursor is delivered via an inert carrier gas.It may be difficult to obtain a purely anhydrous solvent for use in aliquid-phase treatment. Water in the bulk phase during treatment mayresult in clump deposition, which will adversely affect the finalquality or coverage of the coating. In an embodiment of a vapor-phaseprocess, the template is placed in a vacuum chamber, after which thechamber is cycle-purged to remove excess water. Some adsorbed water,however, remains on the surface of the template. A small amount ofwater, however, is believed to be needed to initiate a surface reaction,which forms the coating. It is believed that the reaction may bedescribed by the formula:R—SiCl₃+3H₂O═>R—Si(OH)₃+3HCl

To facilitate the reaction, the template is brought to a desiredreaction temperature via a temperature-controlled chuck. The precursoris then fed into the reaction chamber for a prescribed time. Reactionparameters such as template temperature, precursor concentration, flowgeometries, etc. are tailored to the specific precursor and templatesubstrate combination. By controlling these conditions, the thickness ofthe surface treatment layer is controlled. The thickness of the surfacetreatment layer is kept at a minimal value to minimize the interferenceof the surface treatment layer with the feature size. In one embodiment,a monolayer of the surface treatment layer is formed.

Discontinuous Template

In an embodiment, there are at least two separate depths associated withthe recesses on the lower surface of the template. FIGS. 20A and 20Bdepict top and cross-sectional views, respectively, of a patternedtemplate with recesses having two depths. Referring to FIGS. 20A and20B, a template includes one or more patterning areas 401. In suchembodiments, a first relatively shallow depth is associated with therecesses in the patterning areas of the template, as depicted in FIG.20B. The patterning area includes the area replicated during patterningof the template. The patterning areas are positioned within a regiondefined by border 409 of the template. Border 409 is defined as theregion that extends from an outer edge of any of the patterning areas toan edge 407 of the template. The border has a depth that issubstantially greater than the depth of the recesses in the patterningareas. The perimeter of the template is herein defined as the boundarybetween the patterning areas and border 409. As depicted in FIG. 20Afour patterning areas are positioned within the area defined by thetemplate. The patterning areas are separated from edges 407 of thetemplate by border 409. The “perimeter” of the template is defined byedges 403 a, 403 b, 403 c, 403 d, 403 e, 403 f, 403 g, and 403 h of thepatterning areas.

The patterning areas may be separated from each other by channel regions405. Channel regions are recesses that are positioned between thepatterning areas that have a greater depth than the recesses of thepattering areas. As described below, both border regions and channelregions inhibit the flow of liquid between the patterning regions orbeyond the perimeter of the patterning areas, respectively.

The design of the template is chosen based on the type of lithographyprocess used. For example, a template for positive imprint lithographyhas a design that favors the formation of discontinuous films on thesubstrate. In one embodiment, a template 12 is formed such that thedepth of one or more structures is relatively large compared to thedepth of structures used to form the patterning region, as depicted inFIG. 15. During use, template 12 is placed in a desired spacedrelationship to substrate 20. In such an embodiment, the gap (h₁)between the lower surface 536 of template 12 and substrate 20 is muchsmaller than the gap (h₂) between recessed surface 534 and substrate 20.For example, h₁ may be less than about 200 nm, while h₂ may be greaterthan about 10,000 nm. When the template is brought into contact withliquid 40 on substrate 20, liquid 40 leaves the region under recessedsurface 534 and fills the gap between lower surface 536 and substrate 20(as depicted in FIG. 16). It is believed that combinations of surfaceenergies and capillary forces draw the liquid from the larger recessinto the narrower region. As h₁ is decreased, forces applied to theliquid by template 12 may overcome capillary forces drawing the liquidunder lower surface 536. These forces may cause spreading of the liquidinto the area under recessed surface 534. The minimum value of h₁ atwhich the liquid is inhibited from spreading into a recess 532 isreferred to herein as the “minimum film thickness.” Additionally, as h₁increases, the capillary forces are reduced, eventually allowing theliquid to spread into the deeper recessed regions. The maximum value ofh₁ at which the capillary forces are sufficient to inhibit flow ofliquid into the deeper recessed region is herein known as the “maximumfilm thickness.”

As depicted in FIGS. 17 and 18, in various embodiments, template 12 isformed such that a curable liquid placed on substrate 20 is inhibitedfrom flowing beyond perimeter 412 of template 12. In the embodimentdepicted in FIG. 17, height h₁ is measured from substrate 20 to shallowrecessed surface 552. Shallow recessed surface 552 extends to theperimeter of template 12. Thus, the edge of the template forms theheight h₂ and is effectively infinite in comparison to height h₁. In theembodiment depicted in FIG. 18, a deep recess is formed at the outeredge of template 12. Height h₂ is measured between substrate 20 and deeprecessed surface 554. Height h₁ is again measured between substrate 20and shallow recessed surface 552. In either embodiment, height h₂ ismuch larger than height h₁. If h₁ is small enough, the activating lightcurable liquid remains in the gap between template 12 and substrate 20while a curing agent is applied. Deeply recessed portions areparticularly useful for liquid confinement in step and repeat processesas described herein.

In an embodiment, template 12 and substrate 20 each have one or morealignment marks. Alignment marks may be used to align template 12 andsubstrate 20. For example, one or more optical imaging devices (e.g.,microscopes, cameras, imaging arrays, etc.) are used to determinealignment of the alignment marks.

In some embodiments, an alignment mark on the template may besubstantially transparent to activating light. Alternatively, thealignment mark may be substantially opaque to alignment mark detectionlight. As used herein, alignment mark detection light and light used forother measurement and analysis purposes is referred to as “analyzinglight.” In an embodiment, analyzing light includes, but is not limitedto: visible light and/or infrared light. The alignment mark may beformed of a material different than the material of the body. Forexample, the alignment mark may be formed from SiOx where x is about1.5. In another example, the alignment mark may be formed of molybdenumsilicide. Alternately, the alignment mark may include a plurality oflines etched on a surface of the body. The lines are configured tosubstantially diffuse activating light, but produce an analyzable markunder analyzing light.

In various embodiments, one or more deep recesses as described above mayproject entirely through the body of the template to form openings inthe template. An advantage of such openings is that they may effectivelyensure that height h₂ is very large with respect to h₁ at each opening.Additionally, in some embodiments, pressurized gas or vacuum may beapplied to the openings. Pressurized gas or vacuum may also be appliedto one or more openings after curing the liquid. For example,pressurized gas may be applied after curing as part of a peel and pullprocess to assist in separating the template from the cured liquid.

Alternate System Embodiments

The above described imprint lithography system may be modified accordingto alternate embodiments discussed below. It should be understood thatany of the described alternative embodiments may be combined, singly orin combination, with any other system described herein.

As described above, an imprint head includes a fine orientation systemthat allows for a “passive” orientation of the template with respect tothe substrate. In another embodiment, fine orientation system mayinclude actuators coupled to the flexure arms. The actuators may allow“active” control of the fine orientation system. During use an operatoror a programmable controller monitors the orientation of the templatewith respect to the substrate. The operators or a programmablecontroller then alters the orientation of the template with respect tothe substrate by operating the actuators. Movement of the actuatorscauses motion of the flexure arms to alter the orientation of thetemplate. In this manner an “active” control of fine positioning of thetemplate with respect to the substrate may be achieved. An active fineorientation system is further described in U.S. Ser. No. 09/920,341filed Aug. 1, 2001 (published as U.S. Publication No. 2002-0093122)entitled “Methods for High-Precision Gap Orientation Sensing Between aTransparent Template and Substrate for Imprint Lithography,” which isincorporated herein by reference.

In an alternate embodiment, imprint head may include a pre-calibrationsystem, as described above. Pre-calibration system includes a flexurering 3124 as depicted in FIG. 21. In place of the fine orientationsystem as described above, a template support system 3125 is coupled topre-calibration ring. In contrast to the fine orientation system,template support system 3125 is formed of substantially rigid andnon-compliant members 3127. These members provide a substantially rigidsupport for a template 3700 disposed in template support 3130. In thisembodiment, fine orientation may be achieved using motion stage insteadof template support.

In previous embodiments, imprint head 3100 is coupled to the body in afixed position. In an alternate embodiment, imprint head 3100 may bemounted to a motion system that allows the imprint head to be movedalong the X-Y plane, as depicted in FIG. 22. Imprint head 3100 isconfigured to support a patterned template as described in any of theembodiments herein. Imprint head 3100 is coupled to a motion system thatincludes imprint head chuck 3121 and imprint motion stage 3123. Imprinthead 3100 is mounted to imprint head chuck 3121. Imprint head chuck 3121interacts with an imprint motion stage 3123 to move imprint head 3100along an X-Y plane. Mechanical or electromagnetic motion systems may beused. Electromagnetic systems rely on the use of magnets to produce anX-Y planar motion on the imprint head chuck 3121. Generally, anelectromagnetic system incorporates permanent and electromagneticmagnets into the imprint motion stage 3123 and the imprint head chuck3121. The attractive forces of these magnets is overcome by a cushion ofair between imprint head chuck 3121 and imprint head motion stage 3123such that an “air bearing” is produced. Imprint head chuck 3121, andtherefore the imprint head 3100, is moved along an X-Y plane on acushion of air. Electromagnetic X-Y motion stages are described infurther detail in U.S. Pat. No. 6,389,702, entitled “Method andApparatus for Motion Control,” which is incorporated herein byreference. In a mechanical motion system, imprint head chuck 3121 isattached to motion stage 3123. Motion stage 3123 is then moved by use ofvarious mechanical means to alter the position of imprint head chuck3121, and thus imprint head 3100, along the X-Y plane. In thisembodiment, imprint head 3100 may include a passive compliant fineorientation system, an actuated fine orientation system, or a rigidtemplate support system, as described herein.

With imprint head 3100 coupled to a moving support, the substrate may bemounted to a stationary support. Thus, in an alternate embodiment,imprint head 3100 is coupled to an X-Y axis motion stage as describedherein. A substrate is mounted to a substantially stationary substratesupport. A stationary substrate support is depicted in FIG. 40.Stationary substrate support 3640 includes a base 3642 and a substratechuck 3644. Substrate chuck 3644 is configured to support a substrateduring imprint lithography processes. Substrate chuck may employ anysuitable means to retain a substrate to the substrate chuck. In oneembodiment, substrate chuck 3644 may include a vacuum system whichapplies a vacuum to the substrate to couple the substrate to thesubstrate chuck. Substrate chuck 3644 is coupled to a base 3642. Base3642 is coupled to support 3920 of an imprint lithography system (SeeFIG. 1). During use, stationary substrate support 3640 remains in afixed position on support 3920 while the imprint head position is variedto access different portions of the substrate.

Coupling an imprint head to a motion stage can offer advantages overtechniques in which the substrate is on a motion stage. Motion stagesgenerally rely on an air bearing to allow substantially frictionlessmotion of the motion stage. Generally, motion stages are not designed toaccommodate significant pressure applied along the Z-axis. When pressureis applied to a motion stage chuck along the Z-axis, the motion stagechuck position will change slightly in response to this pressure. Duringa step and repeat process, a template that has a smaller area than thearea of the substrate is used to form multiple imprinted areas. Thesubstrate motion stage is relatively large compared to the template, toaccommodate the larger substrates. When a template contacts thesubstrate motion stage in a position that is off-center, the motionstage will tilt to accommodate the increased pressure. This tilt iscompensated for by tilting the imprint head to ensure proper alignment.If, however, the imprint head is coupled to the motion stage, all of theforces along the Z-axis will be centered on the template, regardless ofwhere on the substrate the imprinting is taking place. This leads toincreased ease in alignment and may also increase the throughput of thesystem.

In an embodiment, a substrate tilt module may be formed in a substratesupport as depicted in FIG. 39. Substrate support 3650 includes asubstrate chuck 3652, coupled to a substrate tilt module 3654. Substratetilt module 3654 is coupled to a base 3656. Base 3656, in oneembodiment, is coupled to a motion stage which allows X-Y motion of thesubstrate support. Alternatively, base 3656 is coupled to a support(e.g., 3920) such that the substrate support is mounted to an imprintsystem in a fixed position.

Substrate chuck 3652 may employ any suitable means to retain a substrateto the substrate chuck. In one embodiment, substrate chuck 3654 mayinclude a vacuum system which applies a vacuum to the substrate tocouple the substrate to the substrate chuck. Substrate tilt module 3654includes a flexure ring 3658 coupled to flexure ring support 3660. Aplurality of actuators 3662 are coupled to flexure ring 3658 and flexurering support 3660. Actuators 3662 are operated to alter the tilt offlexure ring 3658. Actuators, in one embodiment, use a differential gearmechanism that may be manually or automatically operated. In analternate embodiment, actuators use an eccentric roller mechanism. Aneccentric roller mechanism generally provides more vertical stiffness tothe substrate support than a differential gear system. In oneembodiment, substrate tilt module 3654 has a stiffness that will inhibittilt of the substrate when the template applies a force of between about1 lb. to about 10 lbs. to a liquid disposed on the substrate.Specifically, substrate tilt module 3654 is configured to allow no morethan 5 micro radians of tilt when pressure up to about 10 lbs. isapplied to the substrate through the liquid on the template.

During use sensors coupled to the substrate chuck may be used todetermine the tilt of the substrate. The tilt of the substrate isadjusted by actuators 3662. In this manner tilt correction of thesubstrate may be achieved.

Substrate tilt module may also include a fine orientation system. Asubstrate support that includes a fine orientation system is depicted inFIG. 38. To achieve fine orientation control, flexure ring 3658 includesa central recess in which substrate chuck 3652 is disposed. The depth ofthe central recess is such that an upper surface of a substrate disposedon substrate chuck 3652 is substantially even with an upper surface offlexure ring 3658. Fine orientation may be achieved using actuators3662. Fine orientation is achieved by the use of actuators capable ofcontrolled motion in the nanometer range. Alternatively, fineorientation may be achieved in a passive manner. Actuators may besubstantially compliant. The compliance of the actuators may allow thesubstrate to self-correct for variations in tilt when a template is incontact with a liquid disposed on a substrate surface. By disposing thesubstrate in a position that is substantially even with the flexurering, fine orientation may be achieved at the substrate-liquid interfaceduring use. Compliance of actuators is thus transferred to the uppersurface of the substrate to allow fine orientation of the substrate.

The above-described systems are generally configured to systems in whichan activating light curable liquid is dispensed onto a substrate and thesubstrate and template are brought into proximity to each other. Itshould be understood, however, that the above-described systems may bemodified to allow an activating light curable liquid to be applied to atemplate rather than the substrate. In such an embodiment, the templateis placed below the substrate. FIG. 41 depicts a schematic drawing of anembodiment of a system 4100 that is configured such that the template ispositioned below a substrate. System 4100 includes an imprint head 4110and a substrate support 4120 positioned above imprint head 4110. Imprinthead 4110 is configured to hold a template 3700. Imprint head 4110 mayhave a similar design to any of the herein described imprint heads. Forexample, imprint head 4110 may include a fine orientation system asdescribed herein. Imprint head 4110 may be coupled to imprint headsupport 4130. Imprint head 4110 may be coupled in a fixed position andremain substantially motionless during use. Alternatively, imprint head4110 may be placed on a motion stage that allows X-Y planar motion ofimprint head support 4130 during use.

The substrate to be imprinted is mounted onto a substrate support 4120.Substrate support 4120 has a similar design to any of the hereindescribed substrate supports. For example, substrate support 4120 mayinclude a fine orientation system as described herein. Substrate support4120 may be coupled to a support 4140 in a fixed position and remainsubstantially motionless during use. Alternatively, substrate support4120 may be placed on a motion stage that allows X-Y planar motion ofsubstrate support during use.

During use an activating light curable liquid is placed on a template3700 disposed in imprint head. The template may be patterned or planar,depending on the type of operation to be performed. Patterned templatesmay be configured for use in positive, negative, or combinations ofpositive and negative imprint lithography systems as described herein.

Imprint Lithography Processes

Negative Imprint Lithography Process

A typical imprint lithography process is shown in FIGS. 23A-23F. Asdepicted in FIG. 23A, template 12 is positioned in a spaced relation tothe substrate 20 such that a gap is formed between template 12 andsubstrate 20. Template 12 may include a surface that defines one or moredesired features, which may be transferred to the substrate 20 duringpatterning. As used herein, a “feature size” generally refers to awidth, length and/or depth of one of the desired features. In variousembodiments, the desired features may be defined on the surface oftemplate 12 as recesses and or a conductive pattern formed on a surfaceof the template. Surface 14 of template 12 may be treated with a thinlayer 13 that lowers the template surface energy and assists inseparation of template 12 from substrate 20. Surface treatment layersfor templates are described herein.

In an embodiment, substance 40 may be dispensed upon substrate 20 priorto moving template 12 into a desired position relative to substrate 20.Substance 40 may be a curable liquid that conforms to the shape ofdesired features of template 12. In an embodiment, substance 40 is a lowviscosity liquid that at least partially fills the space of gap 31without the use of high temperatures. Low viscosity liquids may alsoallow the gap between the template and the substrate to be closedwithout requiring high pressures. As used herein the term “low viscosityliquids” refer to liquids having a viscosity of less than about 30centipoise measured at about 25° C. Further details regardingappropriate selections for substance 40 are discussed below. Template 12may interact with curable liquid 40 to conform the liquid into a desireshape. For example, curable liquid 40 may conform to the shape oftemplate 12 as depicted in FIG. 23B. The position of template 12 may beadjusted to create a desired gap distance between the template andsubstrate 20. The position of template 12 may also be adjusted toproperly align the template with the substrate.

After template 12 is properly positioned, substance 40 is cured to forma masking layer 42 on the substrate. In an embodiment, substance 40 iscured using activating light 32 to form masking layer 42. Application ofactivating light through template 12 to cure the liquid is depicted inFIG. 23C. After the liquid is substantially cured, template 12 isremoved from masking layer 42, leaving the cured masking layer on thesurface of substrate 20, as depicted in FIG. 23D. Masking layer 42 has apattern that is complementary to the pattern of template 12. Maskinglayer 42 may include a “base layer” (also called a “residual layer”)between one or more desired features. The separation of template 12 frommasking layer 42 is done so that desired features remain intact withoutshearing or tearing from the surface of substrate 20. Further detailsregarding separation of template 12 from substrate 20 followingimprinting are discussed below.

Masking layer 42 may be used in a variety of ways. For example, in someembodiments, masking layer 42 may be a functional layer. In suchembodiments, curable liquid 40 may be curable to form a conductivelayer, a semiconductive layer, a dielectric layer and/or a layer havinga desired mechanical or optical property. In another embodiment, maskinglayer 42 may be used to cover portions of substrate 20 during furtherprocessing of substrate 20. For example, masking layer 42 may be usedduring a material deposition process to inhibit deposition of thematerial on certain portions of the substrate. Similarly, masking layer42 may be used as a mask for etching substrate 20. To simplify furtherdiscussion of masking layer 42, only its use as a mask for an etchingprocess will be discussed in embodiments described below. However, it isrecognized that masking layers in embodiments described herein may beused in a variety of processes as previously described.

For use in an etch process, masking layer 42 may be etched using an etchprocess until portions of substrate 20 are exposed through masking layer42, as depicted in FIG. 23E. That is, portions of the base layer may beetched away. Portions 44 of masking layer 42 may remain on substrate 20for use in inhibiting etching of portions of substrate 20. After etchingof masking layer 42 is complete, substrate 20 may be etched using knownetching processes. Portions of substrate 20 disposed under portions 44of masking layer 42 may remain substantially unetched while the exposedportions of substrate 20 are etched. In this manner, a patterncorresponding to the pattern of template 12 may be transferred tosubstrate 20. The remaining portions 44 of masking layer 42 may beremoved leaving a patterned substrate 20, depicted in FIG. 23F.

FIGS. 24A-24D illustrate an embodiment of an imprint lithography processusing a transfer layer. A transfer layer 18 may be formed upon an uppersurface of substrate 20. Transfer layer 18 may be formed from a materialthat has different etch characteristics than underlying substrate 20and/or a masking layer formed from a curable liquid 40. That is, eachlayer (e.g., transfer layer 18, masking layer and/or substrate 20) maybe etched at least somewhat selectively with respect to the otherlayers.

A masking layer 44 is formed on the surface of transfer layer 18 bydepositing a curable liquid on the surface of transfer layer 18 andcuring the masking layer as described with reference to FIGS. 23A-23C.Masking layer 42 may be used as a mask for etching transfer layer 18.Masking layer 42 is etched using an etch process until portions oftransfer layer 18 are exposed through masking layer 42, as depicted inFIG. 24B. Portions 44 of masking layer 42 remain on transfer layer 18and may be used to inhibit etching of portions of the transfer layer.After etching of masking layer 42 is complete, transfer layer 18 may beetched using known etching processes. Portions of transfer layer 18disposed under portions 44 of masking layer 42 may remain substantiallyunetched while the exposed portions of transfer layer 18 are etched. Inthis manner, the pattern of masking layer 42 is replicated in transferlayer 18.

In FIG. 24C, portions 44 and etched portions of transfer layer 18together form a masking stack 46 that may be used to inhibit etching ofportions of the underlying substrate 20. Etching of substrate 20 may beperformed using a known etch process (e.g., a plasma etching process, areactive ion etching process, etc.). As depicted in FIG. 24D, themasking stack may inhibit etching of the underlying portions ofsubstrate 20. Etching of the exposed portions of substrate 20 may becontinued until a predetermined depth is reached. An advantage of usinga masking stack as a mask for etching of substrate 20 is that thecombined stack of layers may create a high aspect ratio mask (i.e., amask that has a greater height than width). A high aspect ratio maskinglayer may be desirable during the etching process to inhibitundercutting of the mask portions.

The processes depicted in FIGS. 23A-23F and FIGS. 24A-24D are examplesof negative imprint lithography processes. As used herein a “negativeimprint lithography” process generally refers to a process in which thecurable liquid is substantially conformed to the shape of the templatebefore curing. That is, a negative image of the template is formed inthe cured liquid. As depicted in these figures, the non-recessedportions of the template become the recessed portions of the mask layer.The template, therefore, is designed to have a pattern that represents anegative image of the pattern to be imparted to the mask layer.

Positive Imprint Lithography

As used herein a “positive imprint lithography” process generally refersto a process in which the pattern formed in the mask layer is a mirrorimage of the pattern of the template. As will be further describedbelow, the non-recessed portions of the template become the non-recessedportions of the mask layer.

A typical positive imprint lithography process is shown in FIGS.25A-25D. As depicted in FIG. 25A, template 12 is positioned in a spacedrelation to the substrate 20 such that a gap is formed between template12 and substrate 20. Surface of template 12 may be treated with a thinsurface treatment layer 13 that lowers the template surface energy andassists in separation of template 12 from the cured masking layer.

A curable liquid 40 is disposed on the surface of substrate 20. Template12 is brought into contact with curable liquid 40. As depicted in FIG.25B, the curable liquid fills the gap between the lower surface of thetemplate and the substrate. In contrast to a negative imprintlithography process, curable liquid 40 is substantially absent fromregions of the substrate approximately below at least a portion of therecesses of the template. Thus, curable liquid 40 is maintained as adiscontinuous film on the substrate that is defined by the location ofat least a portion of the recesses of template 12. After template 12 isproperly positioned, curable liquid 40 is cured to form a masking layer42 on the substrate. Template 12 is removed from masking layer 42,leaving the cured masking layer on the surface of substrate 20, asdepicted in FIG. 25C. Masking layer 42 has a pattern that iscomplementary to the pattern of template 12.

Masking layer 42 may be used to inhibit etching of portions of substrate20. After formation of masking layer 42 is complete, substrate 20 may beetched using known etching processes. Portions of substrate 20 disposedunder masking layer 42 may remain substantially unetched while theexposed portions of substrate 20 are etched, as depicted in FIG. 25D. Inthis manner, the pattern of template 12 may be replicated in substrate20. The remaining portions 44 of masking layer 42 may be removed tocreate a patterned substrate 20.

FIGS. 26A-26C illustrate an embodiment of a positive imprint lithographyprocess using a transfer layer. A transfer layer 18 may be formed uponan upper surface of a substrate 20. Transfer layer 18 is formed from amaterial that has different etch characteristics than the underlyingtransfer layer 18 and/or substrate 20. A masking layer 42 is formed onthe surface of transfer layer 18 by depositing a curable liquid on thesurface of transfer layer 18 and curing the masking layer as describedwith reference to FIGS. 25A-25C.

Masking layer 42 may be used as a mask for etching transfer layer 18.Masking layer 42 may inhibit etching of portions of transfer layer 18.Transfer layer 18 may be etched using known etching processes. Portionsof transfer layer 18, disposed under masking layer 42 may remainsubstantially unetched while the exposed portions of transfer layer 18are etched. In this manner, the pattern of masking layer 42 may bereplicated in transfer layer 18.

In FIG. 26B, masking layer 42 and etched portions of transfer layer 18together form a masking stack 46 that may be used to inhibit etching ofportions of the underlying substrate 20. Etching of substrate 20 may beperformed using known etching processes (e.g., a plasma etching process,a reactive ion etching process, etc.). As depicted in FIG. 26C, themasking stack may inhibit etching of the underlying portions ofsubstrate 20. Etching of the exposed portions of substrate 20 may becontinued until a predetermined depth is reached.

Positive/Negative Imprint Lithography

In an embodiment, a process may combine positive and negative imprintlithography. A template for a combined positive and negative imprintlithography process may include recesses suitable for positivelithography and recesses suitable for negative lithography. For example,an embodiment of a template for combined positive and negative imprintlithography is depicted in FIG. 27A. Template 12, as depicted in FIG.27A, includes a lower surface 566, at least one first recess 562, and atleast one second recess 564. First recess 562 is configured to create adiscontinuous portion of curable liquid 40 when the template contactsthe curable liquid. A height of first recess (h.sub.₂) is substantiallygreater than a height of second recess (h.sub.₁)

A typical combined imprint lithography process is shown in FIGS.27A-27D. As depicted in FIG. 27A, template 12 is positioned in a spacedrelation to the substrate 20 such that a gap is formed between template12 and substrate 20. At least the lower surface 566 of template 12 maybe treated with a thin surface treatment layer (not shown) that lowersthe template surface energy and assists in separation of template 12from the cured masking layer. Additionally, surfaces of first recesses562 and/or second recesses 564 may be treated with the thin surfacetreatment layer.

A curable liquid 40 is disposed on the surface of substrate 20. Template12 is brought into contact with curable liquid 40. As depicted in FIG.27B, the curable liquid fills the gap between the lower surface of thetemplate 566 and substrate 20. Curable liquid 40 also fills firstrecesses 562. However, curable liquid 40 is substantially absent fromregions of the substrate approximately below second recesses 564. Thus,curable liquid 40 is maintained as a discontinuous film on the substratethat includes surface topography corresponding to the pattern formed byfirst recesses 562. After template 12 is properly positioned, curableliquid 40 is cured to form a masking layer 42 on the substrate. Template12 is removed from masking layer 42, leaving the cured masking layer onthe surface of substrate 20, as depicted in FIG. 27C. Mask layer 42 mayinclude a region 568 that resembles a mask layer formed by negativeimprint lithography. In addition, mask layer 42 may include a region 569that does not include any masking material.

In one embodiment, mask layer 42 is composed of a material that has thesame or a similar etch rate as the underlying substrate. An etch processis be applied to masking layer 42 to remove the masking layer andsubstrate at substantially the same etch rate. In this manner themultilayer pattern of the template may be transferred to the substrate,as depicted in FIG. 27D. This process may also be performed using atransfer layer as described in other embodiments.

A combination of positive and negative lithography is also useful forpatterning multiple regions of a template. For example, a substrate mayinclude a plurality of regions that require patterning. As depicted inFIG. 27C, a template with multiple depth recesses includes twopatterning regions 568 with an intervening “channel” region 569. Channelregion 569 inhibits flow of a liquid beyond the patterning area of thetemplate.

Step and Repeat

As used herein, a “step and repeat” process refers to using a templatesmaller than the substrate to form a plurality of patterned regions onthe substrate. A step and repeat imprint process includes depositing alight curable liquid on a portion of a substrate, aligning a pattern inthe cured liquid to previous patterns on the substrate, impressing atemplate into the liquid, curing the liquid, and separating the templatefrom the cured liquid. Separating the template from the substrate mayleave an image of the topography of the template in the cured liquid.Since the template is smaller than the total surface area of thesubstrate, only a portion of the substrate includes the patterned curedliquid. The “repeat” portion of the process includes depositing a lightcurable liquid on a different portion of the substrate. A patternedtemplate is then aligned with the substrate and contacted with thecurable liquid. The curable liquid is cured using activating light toform a second area of cured liquid. This process may be continuallyrepeated until most of the substrate is patterned. Step and repeatprocesses may be used with positive, negative, or positive/negativeimprint processes. Step and repeat processes may be performed with anyembodiments of equipment described herein.

Step and repeat imprint lithography processes offer a number ofadvantages over other techniques. Step and repeat processes describedherein are based on imprint lithography that uses low viscosity lightcurable liquids and rigid, transparent templates. The templates aretransparent to liquid activating light and alignment mark detectionlight thus offering the potential for layer-to-layer alignment. Forproduction-scale imprint lithography of multi-level devices, it isadvantageous to possess very high-resolution layer-to-layer alignment(e.g., as low as ⅓ of the minimum feature size (“MFS”)).

There are various sources of distortion errors in making of thetemplates. Step and repeat processes are used so that only a portion ofa substrate is processed during a given step. The size of the fieldprocessed during each step should be small enough to possess patterndistortions of less than ⅓ the MFS. This necessitates step and repeatpatterning in high-resolution imprint lithography. This is also thereason why most optical lithography tools are step and repeat systems.Also, as discussed before, a need for low CD variations and defectinspection/repair also favors processing of small fields.

In order to keep process costs low, it is important for lithographyequipment to possess sufficiently high throughput. Throughputrequirements put a stringent limit on the patterning time allowed perfield. Low viscosity liquids that are light curable are attractive froma throughput point of view. These liquids move much faster to properlyfill the gap between the template and the substrate and the lithographycapability is pattern independent. The resulting low pressure, roomtemperature processing is suitable for high throughput, while retainingthe benefits of layer-to-layer alignment.

While prior inventions have addressed patterning of low viscosity lightcurable liquids, they have not addressed this for a step and repeatprocess. In photolithography as well as in hot embossing, a film is spincoated and hard baked onto the substrate prior to its patterning. Ifsuch an approach is used with low viscosity liquids, there are threemajor problems. Low viscosity liquids are difficult to spin coat sincethey tend to de-wet and cannot retain the form of a continuous film.Also, in a step and repeat process, the liquid undergoes evaporationthereby causing varying amounts of liquid to be left behind on thesubstrate as the template steps and repeats over the substrate. Finally,a blanket light exposure tends to disperse beyond the specific fieldbeing patterned. This tends to cause partial curing of the subsequentfield, thereby affecting the fluid properties of the liquid prior toimprinting. An approach that dispenses liquid suitable for a singlefield onto the substrate, one field at a time, may solve the above threeproblems. However, it is important to accurately confine the liquid tothat particular field to avoid loss of usable area on the substrate.

In general, lithography is one of many unit processes used in theproduction of devices. The cost of all these processes, particularly inmulti-layer devices, makes it highly desirable to place patternedregions as close as possible to each other without interfering withsubsequent patterns. This effectively maximizes the usable area andhence the usage of the substrate. Also, imprint lithography may be usedin a “mix-and-match” mode with other kinds of lithography (such asoptical lithography) wherein different levels of the same device aremade from different lithography technologies. It is advantageous to makethe imprint lithography process compatible with other lithographytechniques. A “kerf” region is the region that separates two adjacentfields on a substrate. In state-of-the-art optical lithography toolsthis kerf region may be as small as 50-100 microns. The size of the kerfis typically limited by the size of the blades used to separate thepatterned regions. This small kerf region is expected to get smaller asthe dicing blades that dice the individual chips get thinner. In orderto accommodate this stringent kerf size requirement, the location of anyexcess liquid that is expelled from the patterned area should be wellconfined and repeatable. As such, the individual components, includingthe template, substrate, liquid and any other materials that affect thephysical properties of the system, including but not limited to surfaceenergy, interfacial energies, Hamacker constants, Van der Waals' forces,viscosity, density, opacity, etc., are engineered as described herein toproperly accommodate a repeatable process.

Formation of Discontinuous Films

As discussed previously, discontinuous films are formed using anappropriately patterned template. For example, a template with highaspect ratio recesses that define a border region can inhibit the flowof a liquid beyond the border area. The inhibition of the liquid withina border area is influenced by a number of factors. As discussed abovetemplate design plays a role in the confinement of a liquid.Additionally, the process by which the template is contacted with theliquid also influences the confinement of the liquid.

FIGS. 19A-19C depict a cross-sectional view of a process whereindiscontinuous films are formed on a surface. In one embodiment, acurable liquid 40 is dispensed onto a substrate 20 as a pattern of linesor droplets, as depicted in FIG. 19A. Curable liquid 40, therefore, doesnot cover an entire area of substrate 20 to be imprinted. As the lowersurface 536 of template 12 contacts liquid 40, the force of the templateon the liquid causes the liquid to spread over the surface of substrate20, as depicted in FIG. 19B. Generally, the more force that is appliedby the template to the liquid, the further the liquid will spread overthe substrate. Thus, if a sufficient amount of force is applied, theliquid may be forced beyond a perimeter of the template, as depicted inFIG. 19C. By controlling the forces applied to the liquid by thetemplate, the liquid is confined within the predetermined borders of thetemplate, as depicted in FIG. 19D.

The amount of force applied to the liquid is related to the amount ofliquid dispensed on the substrate and the distance the template is fromthe substrate during curing. For a negative imprint lithography processthe amount of fluid dispensed onto the substrate should be less than orequal to a volume defined by: the volume of liquid required tosubstantially fill the recesses of the patterned template, the area ofthe substrate to be patterned, and the desired thickness of the curedlayer. If the amount of cured liquid exceeds this volume, the liquidwill be displaced from the perimeter of the template when the templateis brought to the appropriate distance from the substrate. For apositive imprint lithography process the amount of liquid dispensed ontothe substrate should be less than the volume defined by: the desiredthickness of the cured layer (i.e., the distance between thenon-recessed portions of the template and the substrate and the surfacearea of the portion of the substrate to be patterned.

For an imprint lithography process that uses a template that includes aborder, the distance between the non-recessed surface of the templateand the substrate is set between the minimum film thickness and themaximum film thickness, as previously described. Setting the heightbetween these values allows the appropriate capillary forces to containthe liquid within the border defined areas of the template.Additionally, the thickness of the layer should be approximatelycomparable to the height of the patterned features. If the cured layeris too thick, the features formed in the cured layer may be erodedbefore the features can be transferred to the underlying substrate. Itis therefore desirable to control the volume as described above to fallto allow the appropriate film thickness to be used.

The force applied by the template to the liquid is also influenced bythe rate at which the template is brought into contact with the liquid.Generally, the faster the template is brought into contact the moreforce is applied to the liquid. Thus, some measure of control of thespread of liquid on the surface of the substrate may be achieved bycontrolling the rate at which the template is brought into contact withthe liquid.

All of these features are considered when positioning the template withrespect to the substrate for an imprint lithography process. Bycontrolling these variables in a predetermined manner, the flow ofliquid may be controlled to stay confined within a predetermine area.

Alignment Techniques

Overlay alignment schemes include measurement of alignment errorsfollowed by compensation of these errors to achieve accurate alignmentof a patterned template and a desired imprint location on a substrate.Correct placement of the template with respect to the substrate isimportant for achieving proper alignment of the patterned layer with anypreviously formed layers on the substrate. Placement error, as usedherein, generally refers to X-Y positioning errors between a templateand substrate (that is, translation along the X and/or Y-axis).Placement errors, in one embodiment, are determined and corrected for byusing a through the template optical device, as depicted in FIG. 14.

FIG. 28 illustrates a schematic diagram of an optical system 3820 ofthrough the template optical imaging system 3800 (See also FIG. 14).Optical system 3820 is configured to focus two alignment marks fromdifferent planes onto a single focal plane. Optical system 3820 may usethe change of focal length resulting from light with distinctwavelengths to determine the alignment of the template with anunderlying substrate. Optical system 3820 may include an optical imagingdevice 3810, an illumination source (not shown), and a focusing device3805. Light with distinct wavelengths may be generated either by usingindividual light sources or by using a single broad band light sourceand inserting optical band-pass filters between the imaging plane andthe alignment marks. Depending on the gap between the template 3700 andsubstrate 2500, different wavelengths are selected to adjust the focallengths. Under each wavelength of light used, each overlay mark mayproduce two images on the imaging plane as depicted in FIG. 29. A firstimage 2601, using a specific wavelength of light, is a clearly focusedimage. A second image 2602, using the same wavelength of light, is anout-of-focus image. In order to eliminate each out-of-focus image,several methods may be used.

In a first method, under illumination with a first wavelength of light,two images may be received by optical imaging device 3810. Images aredepicted in FIG. 29 and generally referenced by numeral 2604. Whileimages are depicted as squares, it should be understood that any othershape may be used, including crosses. Image 2602 corresponds to anoverlay alignment mark on the substrate. Image 2601 corresponds to anoverlay alignment mark on the template. When image 2602 is focused,image 2601 is out of focus. In an embodiment, an image processingtechnique may be used to erase geometric data corresponding to pixelsassociated with image 2602. Thus, the out-of-focus image of thesubstrate mark may be eliminated, leaving only image 2601. Using thesame procedure and a second wavelength of light, image 2605 and 2606 maybe formed on optical imaging device 3810. The out-of-focus image 2606 isthen eliminated, leaving only image 2605. The two remaining focusedimages 2601 and 2605 are then combined onto a single imaging plane 2603for making overlay error measurements.

A second method may utilize two coplanar polarizing arrays, as depictedin FIG. 30, and polarized illumination sources. FIG. 30 illustratesoverlay marks 2701 and orthogonally polarized arrays 2702. Polarizingarrays 2702 are formed on the template surface or placed above thesurface. Under two polarized illumination sources, only focused images2703 (each corresponding to a distinct wavelength and polarization) mayappear on the imaging plane. Thus, out of focus images are filtered outby polarizing arrays 2702. An advantage of this method may be that itmay not require an image processing technique to eliminate out-of-focusimages.

Moiré pattern based overlay measurement has been used for opticallithography processes. For imprint lithography processes, where twolayers of Moiré patterns are not on the same plane but still overlappedin the imaging array, acquiring two individual focused images may bedifficult to achieve. However, carefully controlling the gap between thetemplate and substrate within the depth of focus of the opticalmeasurement tool and without direct contact between the template andsubstrate may allow two layers of Moiré patterns to be simultaneouslyacquired with minimal focusing problems. It is believed that otherstandard overlay schemes based on the Moiré patterns may be directlyimplemented to imprint lithography process.

Another concern with overlay alignment for imprint lithography processesthat use UV curable liquid materials may be the visibility of thealignment marks. For the overlay placement error measurement, twooverlay marks, one on the template and the other on substrate are used.However, since it is desirable for the template to be transparent to acuring agent, the template overlay marks, in some embodiments, are notopaque lines. Rather, the template overlay marks are topographicalfeatures of the template surface. In some embodiment, the marks are madeof the same material as the template. In addition, UV curable liquidsmay have a refractive index that is similar to the refractive index ofthe template materials (e.g., quartz). Therefore, when the UV curableliquid fills the gap between the template and the substrate, templateoverlay marks may become very difficult to recognize. If the templateoverlay marks are made with an opaque material (e.g., chromium), the UVcurable liquid below the overlay marks may not be properly exposed tothe UV light.

In an embodiment, overlay marks are used on the template that are seenby the optical imaging system 3800 but are opaque to the curing light(e.g., UV light). An embodiment of this approach is illustrated in FIG.31. In FIG. 31, instead of completely opaque lines, overlay marks 3102on the template may be formed of fine polarizing lines 3101. Forexample, suitable fine polarizing lines have a width about ½ to ¼ of thewavelength of activating light used as the curing agent. The line widthof polarizing lines 3101 should be small enough so that activating lightpassing between two lines is diffracted sufficiently to cause curing ofall the liquid below the lines. In such an embodiment, the activatinglight may be polarized according to the polarization of overlay marks3102. Polarizing the activating light provides a relatively uniformexposure to all the template regions including regions having overlaymarks 3102. Light used to locate overlay marks 3102 on the template maybe broadband light or a specific wavelength that may not cure the liquidmaterial. This light need not be polarized. Polarized lines 3101 aresubstantially opaque to the measuring light, thus making the overlaymarks visible using established overlay error measuring tools. Finepolarized overlay marks are fabricated on the template using existingtechniques, such as electron beam lithography.

In another embodiment, overlay marks are formed of a different materialthan the template. For example, a material selected to form the templateoverlay marks may be substantially opaque to visible light, buttransparent to activating light used as the curing agent (e.g., UVlight). For example, SiOx where X is less than 2 may be used as such amaterial. In particular, structures formed of SiOx where X is about 1.5are substantially opaque to visible light, but transparent to UV curinglight.

Liquid Dispensing Patterns

In all embodiments of an imprint lithography process, a liquid isdispensed onto a substrate. While the following description is directedto dispensing liquids on substrate, it should be understood that thesame liquid dispensing techniques are also used when dispensing liquidsonto a template. Liquid dispensing is a carefully controlled process. Ingeneral, liquid dispensing is controlled such that a predeterminedamount of liquid is dispensed in the proper location on the substrate.Additionally, the volume of liquid is also controlled. The combinationof the proper volume of liquid and the proper location of the liquid iscontrolled by using the liquid dispensing systems described herein. Stepand repeat processes, in particular, use a combination of liquid volumecontrol and liquid placement to confine patterning to a specified field.

A variety of liquid dispensing patterns are used. Patterns may be in theform continuous lines or patterns of droplets of liquid. In someembodiments, relative motion between a displacement based liquiddispenser tip and an imprinting member is used to form a pattern withsubstantially continuous lines on a portion of the imprinting member.Balancing rates of dispensing and relative motion is used to control thesize of the cross-section of the line and the shape of the line. Duringthe dispensing process, the dispenser tips are fixed near (e.g., on theorder of tens of microns) to the substrate. Two examples of continuouspatterns are depicted in FIGS. 32A and 32B. The pattern depicted inFIGS. 32A and 32B is a sinusoidal pattern; however, other patterns arepossible. As depicted in FIGS. 32A and 32B continuous line pattern maybe drawn using either a single dispenser tip 2401 or multiple dispensertips 2402. Alternatively, a pattern of droplets may be used, as depictedin FIG. 32C. In one embodiment, a pattern of droplets that has a centraldroplet that has a greater volume than surrounding droplets is used.When the template contacts the droplets, the liquid spreads to fill thepatterning area of the template as indicated in FIG. 32C.

Dispensing rate, v_(d), and relative lateral velocity of an imprintingmember, v_(s), may be related as follows:v _(d) =V _(d) /t _(d) (dispensing volume/dispensing period),  (1)v _(s) =L/t _(d) (line length/dispensing period),  (2)v _(d) =aL (where, ‘a’ is the cross section area of line pattern),  (3)Therefore,v _(d) =av _(s).  (4)

The width of the initial line pattern may normally depend on the tipsize of a dispenser. The dispenser tip may be fixed. In an embodiment, aliquid dispensing controller is used to control the volume of liquiddispensed (V_(d)) and the time taken to dispense the liquid (t_(d)). IfV_(d) and t_(d) are fixed, increasing the length of the line leads tolower height of the cross section of the line patterned. Increasingpattern length may be achieved by increasing the spatial frequency ofthe periodic patterns. Lower height of the pattern may lead to adecrease in the amount of liquid to be displaced during imprintprocesses. By using multiple tips connected to the same dispensing line,line patterns with long lengths may be formed faster as compared to thecase of a single dispenser tip. Alternatively a plurality of closelyspaced drops is used to form a line with an accurate volume.

Separation of Template

After curing of the liquid is completed, the template is separated fromthe cured liquid. Since the template and substrate are almost perfectlyparallel, the assembly of the template, imprinted layer, and substrateleads to a substantially uniform contact between the template and thecured liquid. Such a system may require a large separation force toseparate the template from the cured liquid. In the case of a flexibletemplate or substrate, the separation, in one embodiment, is performedusing a “peeling process.” However, use of a flexible template orsubstrate may be undesirable for high-resolution overlay alignment. Inthe case of a quartz template and a silicon substrate, a peeling processmay be difficult to implement. In one embodiment, a “peel and pull”process is performed to separate the template from an imprinted layer.An embodiment of a peel and pull process is illustrated in FIGS. 33A,33B, and 33C.

FIG. 33A depicts a template 12 embedded in a cured layer 40 aftercuring. After curing of the substance 40, either the template 12 orsubstrate 20 may be tilted to intentionally induce an angle 3604 betweenthe template 12 and substrate 20, as depicted in FIG. 35B. Apre-calibration stage, either coupled to the template or the substratemay be used to induce a tilt between the template and the cured layer40. The relative lateral motion between the template 12 and substrate 20may be insignificant during the tilting motion if the tilting axis islocated close to the template-substrate interface. Once angle 3604between template 12 and substrate 20 is large enough, template 12 may beseparated from the substrate 20 using only Z-axis motion (i.e., verticalmotion). This peel and pull method may result in desired features 44being left intact on a transfer layer 18 and substrate 20 withoutundesirable shearing.

Electrostatic Curing Process

In addition to the above-described embodiments, embodiments describedherein include forming patterned structures by using electric fields.Cured layers formed using electric fields to induce a pattern in thecured layer may be used for single imprinting or step and repeatprocesses.

FIG. 34 depicts an embodiment of template 1200 and substrate 1202.Template 1200, in one embodiment, is formed from a material that istransparent to activating light to allow curing of the polymerizablecomposition by exposure to activating light. Forming template 1200 froma transparent material also allows the use of established opticaltechniques to measure the gap between template 1200 and substrate 1202and to measure overlay marks to perform overlay alignment andmagnification correction during formation of the structures. Template1200 is also thermally and mechanically stable to providenano-resolution patterning capability. Template 1200 includes anelectrically conducting material and/or layer 1204 to allow electricfields to be generated at template-substrate interface.

In one embodiment, a blank of fused silica (e.g., quartz) is used as thematerial for base 1206 of template 1200. Indium Tin Oxide (ITO) isdeposited onto base 1206. ITO is transparent to visible and UV light andis a conducting material. ITO may be patterned using high-resolutionelectron beam lithography. A low-surface energy coating, as previouslydescribed, may be coated onto the template to improve the releasecharacteristics between the template and the polymerized composition.Substrate 1202 may include standard wafer materials such as Si, GaAs,SiGeC and InP. A UV curable liquid and/or a thermally curable liquid maybe used as polymerizable composition 1208. In an embodiment,polymerizable composition 1208 may be spin coated onto the wafer 1210.In another embodiment, a predetermined volume of polymerizablecomposition 1208 may be dispensed onto the substrate in a predeterminedpattern, as described herein. In some embodiments, transfer layer 1212may be placed between wafer 1210 and polymerizable composition 1208.Transfer layer 1212 material properties and thickness may be chosen toallow for the creation of high-aspect ratio structures from low-aspectratio structures created in the cured liquid material. Connecting ITO toa voltage source 1214 may generate an electric field between template1200 and substrate 1202.

In FIGS. 35A-D and FIGS. 36A-C, two embodiments of the above-describedprocess are illustrated. In each embodiment, a desired uniform gap maybe maintained between the template and the substrate. An electric fieldof the desired magnitude may be applied resulting in the attraction ofpolymerizable composition 1208 towards the raised portions 1216 oftemplate 1200. In FIGS. 35A-D, the gap and field magnitudes are suchthat polymerizable composition 1208 makes direct contact and adheres totemplate 1200. A curing agent (e.g., activating light 1218 and/or heat)may be used to cure the liquid. Once desired structures have beenformed, template 1200 may be separated from substrate 1202 by methodsdescribed herein.

In FIGS. 36A-C, the gap and field magnitudes may be chosen such thatpolymerizable composition 1208 achieves a topography that is essentiallythe same as that of template 1200. This topography may be achievedwithout making direct contact with the template. A curing agent (e.g.activating light 1218) may be used to cure the liquid. In the embodimentof FIGS. 35A-D and FIGS. 36A-C, a subsequent etch process may be used toremove the cured material 1220. A further etch may also be used iftransfer layer 1212 is present between cured material 1220 and wafer1210 as shown in FIGS. 35A-D and FIGS. 36A-C.

In another embodiment, FIG. 37A depicts an electrically conductivetemplate that includes a continuous layer of electrically conductiveportions 1504 coupled to a non-conductive base 1502. As shown in FIG.37B the non-conductive portions 1502 of the template are isolated fromeach other by the conductive portions 1504. The template may be used ina “positive” imprint process as described above.

In an embodiment, an “adjustable” template may be used to form a patternon a substrate. The term “adjustable” template, in the context of thisembodiment, generally refers to a template that includes electricallyconductive portions that are independently controlled. Controlling aconductive portion of the template refers to turning on, turning off,and/or adjusting an electric field of the conductive portion. Thisconcept is illustrated in FIG. 38. Template 1700 includes electricallyconductive portions 1702 and non-conductive material 1704.Non-conductive material 1704 insulates conductive portions 1702 fromeach other. Template 1700 is substantially transparent to some or alltypes of activating light. In an embodiment, template 1700 is formedfrom materials that are thermally stable. Conductive portions 1702 maybe formed from, for example, ITO. Non-conductive material 1704 may beformed from, for example, silicon dioxide. Conductive portions 1702 forma pattern complementary to a pattern to be produced on a masking layer.The pattern of conductive portions 1702 is formed in non-conductingmaterial 1704 using methods known to those skilled in the art.Conductive portions 1702 are be electrically connected 1706 to powersource 1708, either independently or together. In an embodiment wherethe conductive portions 1702 are independently connected to power source1708, there may be a control device 1710 to independently adjust theelectric field generated by one or more of conductive portions 1702. Inan embodiment, electrical connectors 1712 run through non-conductivematerial 1704 from another side to connect to conductive portions 1702.In an alternate embodiment, conductive portions 1702 extend throughnonconductive material 1704 such that electrical connectors 1712 are notrequired.

Such embodiments may create lithographic patterned structures quickly(in a time of less than about 1 second). The structures generally havesizes of tens of nanometers. In one embodiment, curing a polymerizablecomposition in the presence of electric fields creates a patterned layeron a substrate. The pattern is created by placing a template withspecific nanometer-scale topography at a controlled distance (e.g.,within nanometers) from the surface of a thin layer of the curableliquid on a substrate. If all or a portion of the desired structures areregularly repeating patterns (such as an array of dots), the pattern onthe template may be considerably larger than the size of the desiredrepeating structures.

The replication of the pattern on the template may be achieved byapplying an electric field between the template and the substrate.Because the liquid and air (or vacuum) have different dielectricconstants and the electric field varies locally due to the presence ofthe topography of the template, an electrostatic force may be generatedthat attracts regions of the liquid toward the template. Surface tensionor capillary pressures tend to stabilize the film. At high electricfield strengths, the polymerizable composition may be made to attach tothe template and dewet from the substrate at certain points. However,the attachment of the liquid film will occur provided the ratio ofelectrostatic forces are comparable to the capillary forces, which ismeasured by the dimensionless number A. The magnitude of theelectrostatic force is approximately εE²d², where E is the permittivityof vacuum, E is the magnitude of the electric field, and d is thefeature size. The magnitude of the capillary forces is approximately γd,where γ is the liquid-gas surface tension. The ratio of these two forcesis Λ=εE²d/T. In order to deform the interface and cause it to attach tothe upper surface, the electric field must be such that L isapproximately unity. The precise value depends on the details of thetopography of the plates and the ratio of liquid-gas permittivities andheights, but this number will be O(1). Thus, the electric field isapproximately given by E˜(γ/εd)^(1/2), This polymerizable compositionmay be hardened in place by polymerization of the composition. Thetemplate may be treated with a low energy self-assembled monolayer film(e.g., a fluorinated surfactant) to aid in detachment of the templatethe polymerized composition.

An example of the above approximations is given below. For d=100 nm andγ=30 mJ/m and ε=8.85×10−12 C²/J−m, E=1.8×10⁸ V/m, which corresponds to apotential difference between the plates of modest 18 V if the platespacing is 100 nm and 180 V is the plate spacing is 1000 nm. Note thatthe feature size d˜γ/εE², which means that the size of the featuredecreases with the square of the electric field. Thus, 50 nm featureswould require voltages on the order of 25 or 250 volts for 100 and 1000nm plate spacings.

It may be possible to control the electric field, the design of thetopography of the template and the proximity of the template to theliquid surface so as to create a pattern in the polymerizablecomposition that does not come into contact with the surface of thetemplate. This technique may eliminate the need for mechanicalseparation of the template from the polymerized composition. Thistechnique may also eliminate a potential source of defects in thepattern. In the absence of contact, however, the liquid may not formsharp, high-resolution structures that are as well defined as in thecase of contact. This may be addressed by first creating structures inthe polymerizable composition that are partially defined at a givenelectric field. Subsequently, the gap may be increased between thetemplate and substrate while simultaneously increasing the magnitude ofthe electric field to “draw-out” the liquid to form clearly definedstructures without requiring contact.

The polymerizable composition may be deposited on top of a transferlayer as previously described. Such a bi-layer process allows low aspectratio, high-resolution structures formed using electrical fields to befollowed by an etch process to yield high-aspect ratio, high-resolutionstructures. Such a bi-layer process may also be used to perform a “metallift-off process” to deposit a metal on the substrate such that themetal is left behind after lift-off in the trench areas of theoriginally created structures.

Using a low viscosity polymerizable composition, pattern formation usingelectric fields may be fast (e.g., less than about 1 sec.), and thestructure may be rapidly cured. Avoiding temperature variations in thesubstrate and the polymerizable composition may also avoid undesirablepattern distortion that makes nano-resolution layer-to-layer alignmentimpractical. In addition, as mentioned above, it is possible to quicklyform a pattern without contact with the template, thus eliminatingdefects associated with imprint methods that require direct contact.

In this patent application, certain U.S. patents and U.S. patentapplications have been incorporated by reference. The text of such U.S.patents and U.S. patent applications is, however, only incorporated byreference to the extent that no conflict exists between such text andthe other statements and drawings set forth herein. In the event of suchconflict, then any such conflicting text in such incorporated byreference U.S. patents and U.S. patent applications is specifically notincorporated by reference in this patent.

While this invention has been described with references to variousillustrative embodiments, the description is not intended to beconstrued in a limiting sense. Various modifications and combinations ofthe illustrative embodiments as well as other embodiments of theinvention, will be apparent to persons skilled in the art upon referenceto the description. It is, therefore, intended that the appended claimsencompass any such modifications or embodiments.

1. A template comprising: a body having a surface with first and secondregions, with said first region having first wetting characteristics fora given material and said second region having second wettingcharacteristics for said given material, with said first wettingcharacteristics differing from said second wetting characteristics. 2.The template as recited in claim 1 where said first region has a firstsurface energy associated therewith and said second region has a secondsurface energy associated therewith that greater than said first surfaceenergy.
 3. The template as recited in claim 1 wherein said first regionincludes a first surface treatment layer and said second region includesa second surface treatment layer.
 4. The template as recited in claim 1further including an additional surface disposed opposite to saidsurface, with said first region being spaced-apart from said additionalsurface a distance greater than a distance that said second region isspaced-apart from said additional surface.
 5. The template as recited inclaim 3 wherein said first region includes a plurality of recesses. 6.The template as recited in claim 3 wherein said second region issubstantially smooth.
 7. The template as recited in claim 1 wherein saidfirst region includes a silynated layer disposed thereon.
 8. Thetemplate as recited in claim 1 wherein said body is formed frommaterials selected from a set of materials consisting essentially ofquartz and fused silica.
 9. The template as recited in claim 1 whereinsaid first region includes a layer of indium tin oxide deposed thereon.10. A template comprising: a body having a surface with first and secondregions, with said first region having a first surface energy associatedtherewith and said second region having a second surface energyassociated therewith that greater than said first surface energy. 11.The template as recited in claim 10 further including an additionalsurface disposed opposite to said surface, with said first region beingspaced-apart from said additional surface a distance greater than adistance that said second region is spaced-apart from said additionalsurface, with said first region including a layer of indium tin oxideand a surface treatment layer, with said layer of indium tin oxide beingdisposed between said additional side and said surface treatment layer.12. The template as recited in claim 11 wherein said surface treatmentlayer comprises a product of a chemical reaction between water andchemicals selected from a set of chemicals consisting essentially ofalkylsilane, fluoroalkylsilane, fluoroalkyltrichlorosilane andtridecafluoro-1,1,2,2-tetrahydrooctyl trichlorosilane.
 13. The templateas recited in claim 10 wherein said template is formed from materialsselected from a set of materials consisting essentially of quartz andfused silica, with said first region having a silynated surfacetreatment layer disposed thereon.
 14. The template as recited in claim13 wherein said second region is exposed portions of said body.
 15. Themethod of claim 10 wherein the first region has a surface energy that is25 dynes/cm to 45 dynes/cm less than a surface energy of said secondregion measured at 250 Celsius.
 16. A template comprising: a body formedfrom fused silica and having a surface with first and second regions,with said first region having a surface treatment layer providing afirst surface energy to facilitate first wetting characteristics for agiven material and said second region being exposed fused-silica havinga second surface energy associated therewith that is greater than saidfirst surface energy to provide said second region with second wettingcharacteristics for said given material.
 17. The template as recited inclaim 16 further including an additional surface disposed opposite tosaid surface, with said first region including a layer of indium tinoxide disposed between said additional side and said surface treatmentlayer.
 18. The template as recited in claim 17 wherein said first regionincludes a plurality of recesses.
 19. The template as recited in claim10 wherein said surface treatment layer is formed of a silynatedcompound.
 20. The template as recited in claim 19 wherein said surfacetreatment layer comprises a product of a chemical reaction between waterand chemicals selected from a set of chemicals consisting essentially ofalkylsilane, fluoroalkylsilane, fluoroalkyltrichlorosilane andtridecafluoro-1,1,2,2-tetrahydrooctyl trichlorosilane.